High intrinsic viscosity melt phase polyester polymers with acceptable acetaldehyde generation rates

ABSTRACT

A method for the production of solid polyester polymer particles comprising:
         a) polycondensing a molten polyester polymer composition in the presence of a polycondensation catalyst composition comprising antimony species;   b) continuing the polycondenzation of the molten polyester polymer composition to an It.V. of 0.68 dL/g or more; and   c) after reaching an It.V. of 0.68 dL/g or more, adding a catalyst stabilizer or deactivator to the polymer melt; and   d) after reaching an It.V. of 0.68 dL/g or more, solidifying the melt into solid polyester polymer particles which do not contain organic acetaldehyde scavengers.       

     In a further embodiment, after solidification of the polyester from the melt phase polycondenzation process:
         e) the amount of residual acetaldehyde in the particles in the solid state is reduced to a level of 10 ppm or less without increasing the It.V. of the particles by more than 0.03 dL/g.       

     Such particles having an AA (acetaldehyde) generation rate of 20 ppm or less upon being melted after solidification following the melt phase production and a free AA level reduced after melt phase production to 10 ppm or less are introduced into a melt processing zone to make articles such as bottle preforms having acceptable levels of residual AA.

The present application is a Divisional application of Ser. No.11/154,208 having a filing date of Jun. 16, 2005.

1. FIELD OF THE INVENTION

The invention pertains to polyester polymers having a high intrinsicviscosity obtained in the melt phase, and more particularly to highintrinsic viscosity polyester polymers polycondensed with an antimonycatalyst in the melt phase having an acceptable acetaldehyde contentafter melt processing without the addition of an acetaldehyde scavenger.

2. BACKGROUND OF THE INVENTION

Polyester polymer made in a melt phase manufacturing process containsacetaldehyde, and such polymers subsequently remelted generateadditional amounts of acetaldehyde. Acetaldehyde is undesirable becauseit imparts a noticeable taste, problematic in carbonated soft drink andwater packaging. The formation of acetaldehyde is a two-step reaction.In the first step, thermal degradation of the polyester chain results inthe creation of acetaldehyde precursors. In the second step,acetaldehyde precursors react to form acetaldehyde. The presence ofacetaldehyde (“AA”) in preforms and bottles can be traced to twosources. The first source of AA is produced in the melt phase processfor manufacturing the polymer. This class of AA is called residual orfree AA and is the actual measurable amount of AA present on or inpolyester polymer pellets that have undergone both AA reaction steps inthe melt phase for making the polyester polymer. However, in the meltphase process for manufacturing the polymer, thermally degradedpolyester chains (first step) produce AA precursors, e.g. species havingvinyl end groups, and not all of these AA precursors progress to thesecond reaction step to form AA in melt phase manufacturing. These AAprecursors as discussed further below may, however, react to form AA ata later time upon remelting the polyester polymer pellets to make moldedarticles.

With all other parameters being equal, the amount of AA generated in themelt phase manufacture and the number of AA precursors made in the meltphase manufacture increases dramatically as the IV (or molecular weight)of the polymer increases. To prevent the build up of AA and AAprecursors to unacceptable levels, the polycondensation of the polymeris continued to a limited extent such that the polymer is made to a lowIV in the melt phase, solidified, and then further polymerized in thesolid state under low oxygen conditions and temperatures sufficientlylow enough to prevent the polymer from melting.

The second source of AA is the additional amount of AA generated whenthe polyester solids are melted in a melt processing zone (e.g. extruderor injection molding machine) by converters to make bottle preforms. AAprecursors present in the solids are converted to AA upon under meltingconditions to generate more AA than originally present in the solidpolyester particles fed to the melt processing zone (second AA reactionstep). In addition, the additional melt history in processing zone canresult in more thermal degradation of the polyester chain (more of thefirst AA reaction step); therefore, additional AA precursors can beformed and react to form AA (more of the second AA step). This phenomenais known as AA generation rate. Thus, it is possible to reduce theamount of residual or free AA present in the pellets to a value of 5 ppmor less, or even 3 ppm or less, and yet produce a preform, made in aninjection molding machine with a barrel temperature of 285° C. and amelt residence time of about 108 seconds, containing higher levels of AAat 13 ppm. When the preforms are blown into bottles, the high AA levelscan adversely impact the taste of the beverage contained in the saidbottles.

There are several causes for the formation of residual AA and AAprecursors which produce high AA generation rates. One cause is that ifthe polycondensation catalyst used in the melt phase is not adequatelystabilized and/or deactivated in the solid polyester polymer, it can,during re-melting in a melt processing zone, continue to catalyze theconversion of AA precursors present in the polymer to form AA duringmelt processing. Adequately stabilizing and/or deactivating thepolycondensation catalyst, therefore, reduces the amount of AA generatedduring melt processing (reduces the AA generation rate), even though AAprecursors may be present in the melt. While catalyst stabilizationand/or deactivation does reduce the AA generated in subsequent meltprocessing steps, some AA is nevertheless generated by virtue of theheat applied to melt the polymer causing more thermal degradation and bya lower level of catalytic activity that may remain to convert some ofthe AA precursor species to AA. Moreover, the ease to which catalystmetals can be deactivated differs from metal to metal. For example, Sbmetal based catalysts require stronger acids at higher levels todeactivate.

Another cause for the formation of residual AA and AA precursors is thethermal degradation of the polyester polymers in the melt phase whichbecomes more prevalent as the IV of the polymer is increased at hightemperatures. When solid-state polymerization is not used to increasethe molecular weight, a longer melt-phase residence time may benecessary to produce the molecular weight needed to blow bottles frompreforms having the required properties. This extended melt-phaseexposure increases the extent of thermal degradation; therefore,producing PET exclusively in the melt phase with acceptable free AAand/or acceptable AA generation rate during subsequent molding is muchmore challenging than the conventional scenario where a portion of themolecular build-up occurs in a solid-phase process. Along with a shortermelt-phase step which generates fewer AA precursors, conventionalprocesses have the added advantage of the solid-stating gas sweepingaway most of the free AA.

The problem of controlling the presence of AA and AA precursors producedin the melt-phase manufacture was discussed in EP 1 188 783 A2,equivalent to U.S. Pat. No. 6,559,271 B2. This patent proposes that theamount of AA and AA precursors can be limited by keeping the reactiontemperature during the entire polycondensation step below 280° C., byusing a highly active titanium catalyst at low dosage to limit theresidence time of the polymer in the melt-phase manufacture, and byusing an excess of AA scavenger added in the melt phase manufacture.Noting that it was particularly important to use highly active catalystsat low reaction temperatures, the use of Sb catalysts was found to be acompromise between reactivity and selectivity, whereas highly activecatalysts such as Ti were found to be a better compromise at low dosagesand low reaction temperatures. To control AA generation from AAprecursors produced in the melt phase manufacture, this patent teachesdeactivating the catalyst with a phosphorus compound late toward orafter the end of polycondensation so as to allow the catalyst to promotethe molecular weight build-up to a intrinsic viscosity (It.V.) of 0.63dL/g and higher. Finally, the amount of the AA scavenger or binder addedmust be in excess so as to bind not only the residual or free AAproduced in the melt phase manufacture, but to also bind whatever AA isgenerated in subsequent melt processing steps.

The problem with the approach of using an acetaldehyde scavenger is thatthey are expensive regardless of when they are added. The problem ofadding acetaldehyde scavengers to the melt phase manufacture is that aportion of the scavenger is consumed by the free acetaldehyde present inthe melt phase manufacture, thereby requiring the addition of an excessamount of scavenger to bind subsequently formed acetaldehyde. As theamount of acetaldehyde scavenger added in the melt phase manufactureincreases, so do costs and the degree of yellow hue imparted to thepolymer by the scavenger, especially if the class of scavengerscontaining amine groups is used. Moreover, the effectiveness of thescavenger may also be impaired by undergoing two heat histories wherethe polyester is molten, especially when one of the heat histories isunder high vacuum, high temperature, and high viscosity conditions (asin the melt phase polycondensation) where the thermal stability of sometypes of scavenger can be compromised and there can be losses due toscavenger volatility. With some scavengers, the amount of yellow colorimparted by the scavenger may increase as the number of melt heathistories increases. It would be desirable, therefore, to produce solidhigh IV polyester polymer particles which do not contain acetaldehydescavengers added in the melt phase yet have both a low AA generationrate and low residual acetaldehyde levels when fed to a subsequent meltprocessing zone.

U.S. Pat. No. 5,898,058 recommends using any one of a large number ofconventional polycondensation catalysts (with combinations of Sbcatalysts and one of Co, Zn, Mg, Mn or Ca based catalysts exemplifiedand/or claimed) in which the catalysts are deactivated late. This patentnotes that the traditional antimony polycondensation catalyst will beginto catalyze or encourage the degradation of the polymer, leading to theformation of acetaldehyde and yellowing of the polymer. Once thepolycondensation reaction essentially reaches completion, furtherreaction allows the catalyst to degrade the polymer and formacetaldehyde and a yellow hue. The patent discloses the manufacture ofpolyester precursors at an It.V. of about 0.64 and 0.62 dL/g, or 0.60dL/g which was increased to an It.V. of 0.81 dL/g by solid statepolymerization. The patent notes that solid state polymerizationtechniques are useful to increase the It.V. of the polyester to thesehigher levels.

It is known that the production of high IV. polyester polymers in themelt phase is problematic because at high temperature, degradationreactions lead to the formation of acetaldehyde and acetaldehydeprecursor formation, and it becomes more difficult to remove AA from themelt as the melt viscosity increases. Consequently, the molecular weightbuild-up in the melt has in the past been limited to a reasonably lownumber (e.g. It.V. of about 0.63 or less), followed by further advancingthe molecular weight of the polymer in the solid state.

However, it would be desirable to obtain the desired high IV entirely inthe melt phase with the elimination of the solid state polymerizationstep so as to avoid the significant equipment and conversion costsassociated with this step. Moreover, high I.V. solid particles producedin the melt phase should have an acceptable AA generation rate for theapplication without the presence of a substance which binds AA duringmelt processing to form articles. Preferably, the solids fed to asubsequent melt processing zone should have an acceptable residualacetaldehyde content for the application without the need for adding anexcess of an acetaldehyde scavenger to the melt phase productionprocess.

3. SUMMARY OF THE INVENTION

There is now provided a simple robust process for making a high IVpolyester polymer without the addition of AA scavengers to the meltphase while providing a particle suitable as a feed to a subsequent meltprocessing zone for making preforms having an acceptable acetaldehydegeneration rate for the application and preferably containing acceptableresidual acetaldehyde for the application. There is now provided amethod for the production of solid polyester polymers comprising addinga stabilizer and/or an Sb catalyst deactivator to a polymer melt havingan It.V. of at least 0.68 dL/g, preferably a phosphorus containingcompound; and subsequently solidifying the melt into solid polyesterpolymer particles or molded articles which do not contain organicacetaldehyde scavengers.

There is also provided a method for the production of solid polyesterpolymer particles comprising:

a) polycondensing a molten polyester polymer composition in the presenceof a polycondensation catalyst composition comprising antimony species;

b) continuing the polycondensation of the molten polyester polymercomposition to an It.V. of 0.68 dL/g or more; and

c) after reaching an It.V. of 0.68 dL/g or more, preferably 0.70 dL/g ormore, and more preferably 0.72 dL/g or more, adding a stabilizer and/oran Sb catalyst deactivator to the polymer melt, preferably a phosphoruscontaining compound; and

d) after reaching an It.V. of 0.68 dL/g or more, solidifying the meltinto solid polyester polymer particles which do not contain organicacetaldehyde scavengers.

Compared to the particles where the addition of thedeactivator/stabilizer in step c) is omitted, the particles produced bythis process preferably have a reduction in AA generation rate of atleast 10% or more, preferably at least 20% or more, more preferably atleast 30% or more, and most preferably of at least 40% or more when madeto It.V.'s of at least 0.68 dL/g. The reduction in AA generation rate iscalculated by subtracting the AA generation rate of the particles withstep c) from the rate of the particles with the stabilizer/deactivatoraddition omitted altogether and all else being equal, dividing thatdifference by the rate with step c) omitted, and multiplying by 100.

Preferably there is also provided an additional process step aftersolidification of the polyester from the melt phase polycondensationprocess in which:

e) the amount of residual acetaldehyde in the solid particles is reducedto a level of 10 ppm or less in the solid state without increasing theIt.V. of the particles by more than 0.03 dL/g.

There is also provided a method for the manufacture of articlescomprising:

-   -   (i) introducing solid polyester polymer particles, having:        -   an It.V. of at least 0.68 dL/g obtained in melt phase            polymerization,        -   a degree of crystallinity of at least 20%,        -   a residual acetaldehyde level of 10 ppm or less,        -   residues of a polycondensation catalyst composition            comprising antimony species,        -   a reduction in acetaldehyde generation rate of at least 20%            or at least 30% or more, or the AA generation rate measured            at 295° C. for 5 minutes is less than 18 ppm, and        -   lacking organic acetaldehyde scavengers,    -   into a melt processing zone and melting the particles to form a        molten polyester polymer composition; and    -   (ii) forming an article comprising a sheet, strand, fiber, or a        molded part from the molten polymer composition.        When the injection molding temperature is 285° C. and the melt        residence time is 108 seconds, performs made from the particles        of this process contain less than or equal to 9 ppm of free AA.        Alternatively, preforms made from the particles of this process        have a reduction in perform AA of at least 10% or more,        preferably at least 20% or more, more preferably at least 30% or        more, and most preferably of at least 40% or more. The reduction        in perform AA is calculated by subtracting the perform AA of the        perform made from particles with step c) from the perform AA of        the perform made from particles with no addition of Sb        stabilizers and/or deactivators and all else being equal,        dividing that difference by the perform AA with step c) omitted,        and multiplying by 100.

The invention has the advantage of making high IV polymers in the meltphase while avoiding the addition of excess acetaldehyde scavengers tothe melt phase which are expensive and contribute to the formation ofcolor bodies. Instead of controlling the formation of acetaldehyde inthe melt-phase manufacture by adding an excess of acetaldehyde scavengeror reducing the It.V. to a low level, polyester polymer solids areproduced in the melt-phase manufacture to have a low acetaldehydegeneration rate while the residual AA formed in the melt phasemanufacture is preferably reduced in the solid particles withoutresorting to solid-state polymerizing the polymer. The preferred processprovides solid particles having a high IV obtained in melt phasemanufacture without acetaldehyde scavengers and which are suitable as afeed to a subsequent melt processing zone for making preforms or otherarticles.

In preferred embodiments, other achievable advantages employ a robustand simple process which allows one the flexibility of avoiding solidstate polymerization so that high levels of phosphorus can be added topromote stabilization and/or catalyst deactivation without concern as tothe impact on solid-state polymerization rate and also allows the use ofantimony-containing catalysts which can produce polymer compositionssuitable to make articles having good brightness (high L* color) andacceptable yellowness (low b* color).

4. DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of the invention.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. For example,reference to processing or making a “polymer,” a “preform,” “article,”“container,” or “bottle” is intended to include the processing or makingof a plurality of polymers, preforms, articles, containers or bottles.References to a composition containing “an” ingredient or “a” polymer isintended to include other ingredients or other polymers, respectively,in addition to the one named.

By “comprising” or “containing” is meant that at least the namedcompound, element, particle, or method step etc. must be present in thecomposition or article or method, but does not exclude the presence ofother compounds, catalysts, materials, particles, method steps, etc.,even if the other such compounds, material, particles, method steps etc.have the same function as what is named, unless expressly excluded inthe claims.

It is also to be understood that the mention of one or more method stepsdoes not preclude the presence of additional method steps before orafter the combined recited steps or intervening method steps betweenthose steps expressly identified. Moreover, the lettering of processsteps is a convenient means for identifying discrete activities orsteps, and unless otherwise specified, recited process steps can bearranged in any sequence. Expressing a range includes all integers andfractions thereof within the range. Expressing a temperature or atemperature range in a process, or of a reaction mixture, or of a meltor applied to a melt, or of a polymer or applied to a polymer means inall cases that the limitation is satisfied if either the appliedtemperature, the actual temperature of the melt or polymer, or both areat the specified temperature or within the specified range.

The It.V. values described throughout this description are set forth indL/g units as calculated from the inherent viscosity measured at 25° C.in 60% phenol and 40% 1,1,2,2-tetrachloroethane by weight. Polymersamples are dissolved in the solvent at a concentration of 0.25 g/50 mL.The viscosity of the polymer solutions is determined using a ViscotekModified Differential Viscometer. A description of the operatingprinciple of the differential viscometers can be found in ASTM D 5225.The inherent viscosity is calculated from the measured solutionviscosity. The following equations describe such solution viscositymeasurements and subsequent calculations to Ih.V. and from Ih.V. toIt.V:η_(inh)=[ln(t _(s) /t _(o))]/C

where

-   -   η_(inh)=Inherent viscosity at 25° C. at a polymer concentration        of 0.5 g/100 mL of 60% phenol and 40% 1,1,2,2-tetrachloroethane        by weight    -   ln=Natural logarithm    -   t_(s)=Sample flow time through a capillary tube    -   t_(o)=Solvent-blank flow time through a capillary tube    -   C=Concentration of polymer in grams per 100 mL of solvent        (0.50%)

The intrinsic viscosity is the limiting value at infinite dilution ofthe specific viscosity of a polymer. It is defined by the followingequation:η_(int)=lim(η_(sp) /C)=lim(lnη_(r))/CC→0 C→0

where

-   -   η_(int)=Intrinsic viscosity    -   η_(r)=Relative viscosity=t_(s)/t_(o)    -   η_(sp)=Specific viscosity=η_(r)−1

Instrument calibration involves triplicate testing of a standardreference material and then applying appropriate mathematical equationsto produce the “accepted” Ih.V. values. The three values used forcalibration shall be within a range of 0.010; if not, correct problemsand repeat testing of standard until three consecutive results withinthis range are obtained.Calibration Factor=Accepted Ih.V. of Reference Material/Average ofTriplicate Determinations

The uncorrected inherent viscosity (η_(inh)) of each sample iscalculated from the Viscotek Model Y501 Relative Viscometer using thefollowing equation:η_(inh)=[ln(P ₂ /KP ₁)]/C

where

-   -   P₂=The pressure in capillary P₂    -   P₁=The pressure in capillary P₁    -   ln=Natural logarithm    -   K=Viscosity constant obtained from baseline reading    -   C=Concentration of polymer in grams per 100 mL of solvent        The corrected Ih.V., based on calibration with standard        reference materials, is calculated as follows:        Corrected Ih.V.=Calculated Ih.V.×Calibration Factor

The intrinsic viscosity (It.V. or η_(int)) may be estimated using theBillmeyer equation as follows:η_(int)=0.5[e ^(0.5×Corrected Ih.V.)−1]+(0.75×Corrected Ih.V.)

The reference for estimating intrinsic viscosity (Billmeyerrelationship) is J. Polymer Sci., 4, pp. 83-86 (1949).

The L* or b* color can be measured from specimens ground to a powder ormade from a disc or from a preform or from a bottle sidewall asexplained below. A specimen is considered to be within a specified L* orb* color range in the appended claims if the reported L* or b* valueobtained from a specimen measured by any one of these test methods iswithin the ranges expressed in the appended claims. For example, a b*color value outside a specified b* range as measured by one test methodbut inside a specified b* range as measured by another test method isdeemed to be a polymer within the specified range because it satisfiedthe specified b* color range by one of the test methods.

The measurements of L* and b* color values are conducted on specimensprepared according to any one of the following methods. Alternatively,color values are measured on polyester polymers ground to a powderpassing a 3 mm screen.

For powdered samples, color measurements were performed in reflectance(specular included) using a HunterLab UltraScan XE (Hunter AssociatesLaboratory, Inc., Reston Va.), which employs diffuse/8°(illumination/view angle) sphere optical geometry. Results were reportedusing the CIELAB scale with the D65 illuminant and 10° observer. Thespectrophotometer is standardized regularly and UV control was employedand maintained in calibration following the HunterLab recommendations.An optional glass port plate is installed at the reflectance port tominimize contamination of the sphere. Powders are placed in an opticalglass cell. The optical-grade glass is recessed from the front of thecell by 0.062″ and the glass itself is 0.092″ thick. The sample area is0.71″ deep, 1.92″ wide, 2.35″ tall. The powders are allowed to settle byvibrating the sample for 20 seconds using a laboratory Mini-Vortexer(VWR International, West Chester, Pa.). The glass cell is maintainedflush against the reflectance port and covered with a black opaquecover. A single cell packing is evaluated and the cell is removed andreplaced for three replicate measurements for each sample. The reportedvalue should be the average of the triplicates.

The invention relates to a method for the production of solid polyesterpolymer particles comprising:

a) polycondensing a molten polyester polymer composition in the presenceof a polycondensation catalyst composition comprising antimony species;

b) continuing the polycondensation of the molten polyester polymercomposition to an It.V. of 0.68 dL/g or more; and

c) after reaching an It.V. of 0.68 dL/g or more, adding an Sb catalyststabilizer and/or deactivator to the polymer melt, preferably aphosphorus containing compound; and

d) after reaching an It.V. of 0.68 dL/g or more, solidifying the meltinto solid polyester polymer particles which do not contain organicacetaldehyde scavengers and optionally but preferably

e) the level of residual acetaldehyde in the solid particles is reduceddown to a level of 10 ppm or less in the solid state without increasingthe It.V. of the particles by more than 0.03 dL/g.

The “polyester polymer” of this invention is any thermoplastic polyesterpolymer. Polyester thermoplastic polymers of the invention aredistinguishable from liquid crystal polymers and thermosetting polymersin that thermoplastic polymers have no appreciable ordered structurewhile in the liquid (melt) phase, they can be remelted and reshaped intoa molded article, and liquid crystal polymers and thermosetting polymersare unsuitable for the intended applications such as packaging orstretching in a mold to make a container. The polyester polymerdesirably contains alkylene terephthalate or alkylene naphthalate repeatunits in the polymer chain. More preferred are polyester polymers whichcomprise:

-   -   (i) a carboxylic acid component comprising at least 80 mole % of        the residues of terephthalic acid, derivates of terephthalic        acid, naphthalene-2,6-dicarboxylic acid, derivatives of        naphthalene-2,6-dicarboxylic acid, or mixtures thereof, and    -   (ii) a hydroxyl component comprising at least 80 mole % of the        residues of ethylene glycol or propane diol,        based on 100 mole percent of carboxylic acid component residues        and 100 mole percent of hydroxyl component residues in the        polyester polymer.

Typically, polyesters such as polyethylene terephthalate are made byreacting a diol such as ethylene glycol with a dicarboxylic acid as thefree acid or its C₁-C₄ dialkyl ester to produce an ester monomer and/oroligomers, which are then polycondensed to produce the polyester. Morethan one compound containing carboxylic acid group(s) or derivative(s)thereof can be reacted during the process. All the compounds that enterthe process containing carboxylic acid group(s) or derivative(s) thereofthat become part of said polyester product comprise the “carboxylic acidcomponent.” The mole % of all the compounds containing carboxylic acidgroup(s) or derivative(s) thereof that are in the product add up to 100.The “residues” of compound(s) containing carboxylic acid group(s) orderivative(s) thereof that are in the said polyester product refers tothe portion of said compound(s) which remains in the said polyesterproduct after said compound(s) is condensed with a compound(s)containing hydroxyl group(s) and further polycondensed to form polyesterpolymer chains of varying length.

More than one compound containing hydroxyl group(s) or derivativesthereof can become part of the polyester polymer product(s). All thecompounds that enter the process containing hydroxyl group(s) orderivatives thereof that become part of said polyester product(s)comprise the hydroxyl component. The mole % of all the compoundscontaining hydroxyl group(s) or derivatives thereof that become part ofsaid polyester product(s) add up to 100. The “residues” of hydroxylfunctional compound(s) or derivatives thereof that become part of saidpolyester product refers to the portion of said compound(s) whichremains in said polyester product after said compound(s) is condensedwith a compound(s) containing carboxylic acid group(s) or derivative(s)thereof and further polycondensed to form polyester polymer chains ofvarying length.

The mole % of the hydroxyl residues and carboxylic acid residues in theproduct(s) can be determined by proton NMR.

In a preferred embodiment, the polyester polymer comprises:

-   -   (a) a carboxylic acid component comprising at least 90 mole %,        or at least 92 mole %, or at least 96 mole % of the residues of        terephthalic acid, derivates of terephthalic acid,        naphthalene-2,6-dicarboxylic acid, derivatives of        naphthalene-2,6-dicarboxylic acid, or mixtures thereof, and    -   (b) a hydroxyl component comprising at least 90 mole %, or at        least 92 mole %, or at least 96 mole % of the residues of        ethylene glycol,        based on 100 mole percent of the carboxylic acid component        residues and 100 mole percent of the hydroxyl component residues        in the polyester polymer.

The reaction of the carboxylic acid component with the hydroxylcomponent during the preparation of the polyester polymer is notrestricted to the stated mole percentages since one may utilize a largeexcess of the hydroxyl component if desired, e.g. on the order of up to200 mole % relative to the 100 mole % of carboxylic acid component used.The polyester polymer made by the reaction will, however, contain thestated amounts of aromatic dicarboxylic acid residues and ethyleneglycol residues.

Derivates of terephthalic acid and naphthalane dicarboxylic acid includeC₁-C₄ dialkylterephthalates and C₁-C₄ dialkylnaphthalates, such asdimethylterephthalate and dimethylnaphthalate.

Modifiers can be present in amount of up to 40 mole %, or up to 20 mole%, or up to 10 mole %, or up to 8 mole %, or up to 4 mole %, based onthe total moles of their respective component in the polymer. Mono, triand higher functional modifiers are preferably present in amounts ofonly up to about 8 mole %, or up to 4 mole %.

In addition to a diacid component of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, the carboxylicacid component(s) of the present polyester may include one or moreadditional modifier carboxylic acid compounds. Such additional modifiercarboxylic acid compounds include mono-carboxylic acid compounds,dicarboxylic acid compounds, and compounds with a higher number ofcarboxylic acid groups. Examples include aromatic dicarboxylic acidspreferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acidspreferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylicacids preferably having 8 to 12 carbon atoms. More specific examples ofmodifier dicarboxylic acids useful as an acid component(s) are phthalicacid, isophthalic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,4-dicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, and the like, with isophthalic acid,naphthalene-2,6-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acidbeing most preferable. It should be understood that use of thecorresponding acid anhydrides, esters, and acid chlorides of these acidsis included in the term “carboxylic acid”. It is also possible fortricarboxyl compound branching agents and compounds with a higher numberof carboxylic acid groups to modify the polyester, along withmonocarboxylic acid chain terminators.

In addition to a hydroxyl component comprising ethylene glycol, thehydroxyl component of the present polyester may include additionalmodifier mono-ols, diols, or compounds with a higher number of hydroxylgroups. Examples of modifier hydroxyl compounds include cycloaliphaticdiols preferably having 6 to 20 carbon atoms and/or aliphatic diolspreferably having 3 to 20 carbon atoms. More specific examples of suchdiols include diethylene glycol; triethylene glycol;1,4-cyclohexanedimethanol; propane-1,3-diol; butane-1,4-diol;pentane-1,5-diol; hexane-1,6-diol; 3-methylpentanediol-(2,4);2-methylpentanediol-(1,4); 2,2,4-trimethylpentane-diol-(1,3);2,5-ethylhexanediol-(1,3); 2,2-diethyl propane-diol-(1,3);hexanediol-(1,3); 1,4-di-(hydroxyethoxy)-benzene;2,2-bis-(4-hydroxycyclohexyl)-propane;2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane. As modifiers, the polyesterpolymer may preferably contain such comonomers as isophthalic acid,naphthalane dicarboxylic acid, 1,4-cyclohexanedimethanol, and diethyleneglycol.

The polyester pellet compositions may include blends of polyalkyleneterephthalates and/or polyalkylene naphthalates along with otherthermoplastic polymers such as polycarbonate (PC) and polyamides. It ispreferred that the polyester composition should comprise a majority ofthe polyester polymers, more preferably in an amount of at least 80 wt.%, or at least 95 wt. %, and most preferably 100 wt. %, based on theweight of all thermoplastic polymers (excluding fillers, inorganiccompounds or particles, fibers, impact modifiers, or other polymerswhich may form a discontinuous phase). It is also preferred that thepolyester polymers do not contain any fillers, fibers, or impactmodifiers or other polymers which form a discontinuous phase.

The polyester compositions can be prepared by polymerization proceduresknown in the art sufficient to effect esterification andpolycondensation. Polyester melt phase manufacturing processes includedirect condensation of a dicarboxylic acid with the diol, optionally inthe presence of esterification catalysts, in the esterification zone,followed by polycondensation in the prepolymer and finishing zones inthe presence of a polycondensation catalyst composition comprisingantimony species; or ester exchange usually in the presence of atransesterification catalyst in the ester exchange zone, followed byprepolymerization and finishing in the presence of a polycondensationcatalyst composition comprising antimony species.

To further illustrate, a mixture of one or more dicarboxylic acids,preferably aromatic dicarboxylic acids, or ester forming derivativesthereof, and one or more diols are continuously fed to an esterificationreactor operated at a temperature of between about 200° C. and 300° C.,and at a super-atmospheric pressure of between about 1 psig up to about70 psig. The residence time of the reactants typically ranges frombetween about one and five hours. Normally, the dicarboxylic acid(s) isdirectly esterified with diol(s) at elevated pressure and at atemperature of about 240° C. to about 285° C.

The esterification reaction is continued until a acid or ester groupconversion of at least 70% is achieved, but more typically until a acidor ester group conversion of at least 85% is achieved to make thedesired oligomeric mixture (or otherwise also known as the “monomer”).The reaction to make the oligomeric mixture is typically uncatalyzed inthe direct esterification process and catalyzed in ester exchangeprocesses. The antimony containing catalyst may optionally be added inthe esterification zone along with raw materials. Typical ester exchangecatalysts which may be used in an ester exchange reaction betweendialkylterephthalate and a diol include titanium alkoxides and dibutyltin dilaurate, zinc compounds, manganese compounds, each used singly orin combination with each other. Any other catalyst materials well knownto those skilled in the art are suitable. In a most preferredembodiment, however, the ester exchange reaction proceeds in the absenceof titanium compounds. Titanium based catalysts present during thepolycondensation reaction negatively impact the b* by making the meltmore yellow. While it is possible to deactivate the titanium basedcatalyst with a stabilizer after completing the ester exchange reactionand prior to commencing polycondensation, in a most preferred embodimentit is desirable to eliminate the potential for the negative influence ofthe titanium based catalyst on the b* color of the melt by conductingthe direct esterification or ester exchange reactions in the absence ofany added titanium containing compounds. Suitable alternative esterexchange catalysts include zinc compounds, manganese compounds, ormixtures thereof.

The resulting oligomeric mixture formed in the esterification zone(which includes direct esterification and ester exchange processes)includes bis(2-hydroxyethyl)terephthalate (BHET) monomer, low molecularweight oligomers, DEG, and trace amounts of water as the condensationby-product not removed in the esterification zone, along with othertrace impurities from the raw materials and/or possibly formed bycatalyzed side reactions, and other optionally added compounds such astoners and stabilizers. The relative amounts of BHET and oligomericspecies will vary depending on whether the process is a directesterification process in which case the amount of oligomeric speciesare significant and even present as the major species, or a esterexchange process in which case the relative quantity of BHETpredominates over the oligomeric species. Water is removed as theesterification reaction proceeds in order to drive the equilibriumtoward the desired products. The esterification zone typically producesthe monomer and oligomer species, if any, continuously in a series ofone or more reactors. Alternately, the monomer and oligomer species inthe oligomeric mixture could be produced in one or more batch reactors.It is understood, however, that in a process for making PEN, thereaction mixture will contain the monomeric speciesbis(2-hydroxyethyl)-2,6-naphthalate and its corresponding oligomers. Atthis stage, the It.V. is usually not measurable or is less than 0.1. Theaverage degree of polymerization of the molten oligomeric mixture istypically less than 15, and often less than 7.0.

Once the oligomeric mixture is made to the desired percent conversion ofthe acid or ester groups, it is transported from the esterification zoneor reactors to the polycondensation zone. The commencement of thepolycondensation reaction is generally marked by either a higher actualoperating temperature than the operating temperature in theesterification zone, or a marked reduction in pressure compared to theesterification zone, or both. In some cases, the polycondensationreaction is marked by higher actual operating temperatures and lower(usually sub-atmospheric) pressures than the actual operatingtemperature and pressure in the esterification zone. Typicalpolycondensation reactions occur at temperatures ranging from about 260°C. and 300° C., and at sub-atmospheric pressure of between about 350mmHg to 0.2 mm Hg. The residence time of the reactants typically rangesfrom between about 2 to about 6 hours. In the polycondensation reaction,a significant amount of glycols are evolved by the condensation of theoligomeric ester species and during the course of molecular weight buildup.

The polycondensation zone is typically comprised of a prepolymer zoneand a finishing zone, although it is not necessary to have split zoneswithin a polycondensation zone. Polycondensation reactions are initiatedand continued in the melt phase in a prepolymerization zone and finishedin the melt phase in a finishing zone, after which the melt issolidified to form the polyester polymer melt phase product, generallyin the form of chips, pellets, or any other shape.

Each zone may comprise a series of one or more distinct reaction vesselsoperating at different conditions, or the zones may be combined into onereaction vessel using one or more sub-stages operating at differentconditions in a single reactor. That is, the prepolymer stage caninvolve the use of one or more reactors operated continuously, one ormore batch reactors, or even one or more reaction steps or sub-stagesperformed in a single reactor vessel. The residence time of the melt inthe finishing zone relative to the residence time of the melt in theprepolymerization zone is not limited. For example, in some reactordesigns, the prepolymerization zone represents the first half ofpolycondensation in terms of reaction time, while the finishing zonerepresents the second half of polycondensation. Other reactor designsmay adjust the residence time between the finishing zone to theprepolymerization zone at about a 1.5:1 ratio or higher. A commondistinction between the prepolymerization zone and the finishing zone inmany designs is that the latter zone frequently operates at a highertemperature and/or lower pressure than the operating conditions in theprepolymerization zone. Generally, each of the prepolymerization and thefinishing zones comprise one or a series of more than one reactionvessel, and the prepolymerization and finishing reactors are sequencedin a series as part of a continuous process for the manufacture of thepolyester polymer.

In the prepolymerization zone, also known in the industry as the lowpolymerizer, the low molecular weight monomers and oligomers in theoligomeric mixture are polymerized via polycondensation to formpolyethylene terephthalate polyester (or PEN polyester) in the presenceof an antimony-containing catalyst. The catalyst composition comprisingSb species may be added in the esterification or polycondensation zones,such as immediately prior to initiating polycondensation, duringpolycondensation, or to the esterification zone prior to initiatingesterification or ester exchange or during or upon completion of theesterification or ester exchange reaction. If the antimony catalyst isnot added in the esterification stage for the manufacture of theoligomeric mixture, it is after esterification and before or duringpolycondensation, and preferably between esterification andpolycondensation or early in the polycondensation, such as to aprepolymerization step (the first stage of polycondensation) to catalyzethe reaction between the monomers and between the low molecular weightoligomers and between each other to build molecular weight and split offthe diol(s) as a by-product. If the antimony containing catalyst isadded to the esterification zone, it is typically blended with thediol(s) and fed into an esterification reactor(s) and/or into a pastetank containing a paste of terephthalic acid and glycol that is fed intothe first esterification reactor.

In another embodiment, the antimony containing catalyst may be added tothe melt phase before the It.V. of the melt exceeds 0.30 dL/g. By addingthe antimony containing catalyst before the It.V. of the melt exceeds0.30 dL/g, inordinately long reaction times are avoided. Preferably, theantimony containing catalyst is added before the It.V. of the meltexceeds 0.2 dL/g.

The molten polyester polymer is polycondensed in the presence of apolycondensation catalyst composition comprising an antimony species.When referencing “antimony,” or any other inorganic catalyst, theantimony or other inorganic catalyst atom is present in any oxidationstate. When referencing “elemental antimony” or any other inorganiccatalyst in its elemental state, the oxidation state is zero.

X-ray fluorescence (XRF) is the analytical technique used to reportcatalyst levels in polymers. By convention, the XRF technique isreferred to as “elemental analysis.” In actuality, the XRF test isunaffected by the oxidation state of an inorganic-containing species;therefore, it can not differentiate between different oxidation states.The stated amount of measured antimony reflects the total antimonycontent, regardless of its oxidation state in the polymer. Measuredantimony levels in the polyester are reported as the amount of Sb atomsin ppm based on the weight of the polymer, and not in terms of levels ofthe antimony compounds added. The preferred amount of antimony catalystadded is that effective to provide an antimony level of between about atleast 100, or at least 180, or at least 200 ppm based on the weight ofthe polyester. For practical purposes, not more than about 500 ppm ofantimony by weight of the resulting polyester is needed. A preferredrange of antimony is from 150 to less than 300 ppm based on the weightof the polyester, and a most preferred range of antimony is from 175 ppmto 275 ppm Sb.

Suitable antimony containing catalysts added to the melt phase are anyantimony containing catalysts effective to catalyze the polycondensationreaction. These include, but are not limited to, antimony (Ill) andantimony (V) compounds recognized in the art and in particular,diol-soluble antimony (III) and antimony (V) compounds, with antimony(Ill) being most commonly used. Other suitable compounds include thoseantimony compounds that react with, but are not necessarily soluble inthe diols prior to reaction, with examples of such compounds includingantimony (III) oxide. Specific examples of suitable antimony catalystsinclude antimony (III) oxide and antimony (III) acetate, antimony (III)glycolates, antimony (III) ethylene glycoxide and mixtures thereof, withantimony (III) oxide being preferred.

Using an antimony based catalyst is advantageous because the finishedarticles made from antimony-catalyzed polymers are usually brighter(higher L* color) or less yellow (lower b* color) than polymerscatalyzed by the more reactive titanium catalyst. Furthermore, the meltphase polycondensation reaction promoted by an antimony catalyst inaccordance with the invention is capable of proceeding within a widerange of operating temperatures and catalyst concentrations, producingamorphous pellets which, when crystallized, maintain an acceptable b*color of the base polyester polymer below +5 (measured without addedcolorants or toners), and with the addition optional toners orcolorants, obtain a b* value of no greater than 3.0, while maintainingan L* brightness of at least 70, or at least 76, or at least 79. Thus,the process of the invention is not restricted to low catalystconcentrations and low polycondensation temperatures as in the case oftitanium catalysts to maintain an acceptable b* color.

In one embodiment, the crystallized polyester polymer obtained by theprocess of the invention has an L* of at least 70, or at least 73, or atleast 76, or at least 79.

Other catalysts which may be optionally present along with antimonyspecies include catalysts containing zinc, cobalt, manganese, tin,germanium, and other known metals. In a preferred embodiment, however,the polycondensation catalyst composition consists essentially ofantimony species, meaning that the amount of other metal species incombination with antimony should not increase the b* of the solidpolyester polymer particles by more than 0.5 CIELAB units under thereaction conditions used relative to a composition made in the absenceof any metal other than Sb under the same reaction conditions. Morepreferably, since titanium is a highly active catalyst metal that leadsto increased color and degradation in the polyester, the amount ofactive titanium present in the polycondensation melt should be less than5 ppm, preferably less than 3 ppm, more preferably less than 1 ppm andmost preferably no titanium catalyst is added to the polycondensationmelt. The amount of titanium added in the esterification zone to promoteester exchange reactions are not counted in the 5 ppm limitation so longas adequate stabilizer is added prior to commencing polycondensation ofthe melt as determined by adding at least a 2:1 molar stoichiometricamount of elemental phosphorus in the stabilizer to elemental titaniumin the catalyst. Calculations in terms of elemental phosphorus andtitanium are not meant to imply the actual oxidation state of theseinorganic species in the polymer. One of the advantages of the preferredprocess lies in the simplicity of manufacturing a polyester polymer bydirect esterification at acceptable rates without the need for employingmore than one catalyst. Accordingly, in a yet more preferred embodiment,the polycondensation takes place in the presence of a polycondensationcatalyst composition consisting exclusively of antimony species, meaningthat no other metal catalyst compounds, such as titanium, gallium,germanium, zinc, manganese, or magnesium, are added in the melt-phasemanufacturing process to actively catalyze the polycondensation reactionin the melt. In yet a more preferred embodiment, no other metalcompounds, including cobalt, are added. It is to be recognized, however,that one or more of metals such as cobalt or manganese will most likelybe present at low levels in the melt because they come as impuritieswith the terephthalic acid composition made from a metal catalyzedliquid phase oxidation process, but in the most preferred embodiment,these metals are not added to the melt phase production process.

The prepolymer polycondensation stage generally employs a series of oneor more vessels and is operated at a temperature of between about 230°C. and 305° C. for a period between about five minutes to four hours.During this stage, the It.V. of the monomers and oligomers are increasedgenerally up to about no more than 0.45 dL/g. The diol byproduct isremoved from the prepolymer melt generally using an applied vacuumranging from 4 to 200 torr to drive the polycondensation of the melt. Inthis regard, the polymer melt is sometimes agitated to promote theescape of the diol from the polymer melt. As the polymer melt is fedinto successive vessels, the molecular weight and thus the meltviscosity, which is related to the intrinsic viscosity, of the polymermelt increases. The pressure of each vessel is generally decreased toallow for a greater degree of polymerization in each successive vesselor in each successive zone within a vessel. To facilitate removal ofglycols, water, alcohols, aldehydes, and other reaction products, thereactors are typically run under a vacuum or purged with an inert gas.Inert gas is any gas which does not cause unwanted reaction or productcharacteristics at reaction conditions. Suitable gases include, but arenot limited to, argon, helium and nitrogen.

Once the desired It.V. in the prepolymerization zone is obtained,generally no greater than 0.45 dL/g, or not greater than 0.3 dL/g, ornot greater than about 0.2 dL/g, the prepolymer is fed from theprepolymer zone to a finishing zone where the second stage ofpolycondensation is continued in one or more finishing vesselsgenerally, but not necessarily, ramped up to higher temperatures thanpresent in the prepolymerization zone, to a value within a range of from250° C. to 310° C., more generally from 270 to 300° C., until the It.V.of the melt is increased to an It.V in the range of from about at least0.68 dL/g, or at least 0.70 dL/g, or at least 0.72 dL/g, or at least0.75 dL/g and up to about 1.2 dL/g.

In one embodiment, the temperature applied to the polymer melt or of thepolymer melt in at least a portion of the polycondensation zone isgreater than 280° and up to about 290° C. In another embodiment, thetemperatures in the finishing zone are, contrary to conventionalpractice, lower than 280° C. in order to avoid rapid increases in therate of AA precursor formation. The final vessel, generally known in theindustry as the “high polymerizer,” “finisher,” or “polycondenser,” isalso usually operated at a pressure lower than used in theprepolymerization zone to further drive off the diol and/or otherbyproducts and increase the molecular weight of the polymer melt. Thepressure in the finishing zone may be within the range of about 0.2 to20 mm Hg, or 0.2 to 10 mm Hg, or 0.2 to 2 mm Hg. Although the finishingzone typically involves the same basic chemistry as the prepolymer zone,the fact that the size of the molecules, and thus the viscosity differs,means that the reaction conditions also differ. However, like theprepolymer reactor, each of the finishing vessel(s) is operated undervacuum or inert gas, and each is typically but not necessarilymechanically agitated to facilitate the removal of the diol and/or otherbyproducts

In the process of the invention, the residence time of the polymer meltin finishing zone of polycondensation is sufficient to make a polymerhaving an It.V. of at least 0.68 dL/g. The reaction time of the meltfrom an It.V. of 0.40 dL/g through and up to an It.V. in the range of atleast 0.68 dL/g to 0.80 dL/g is 150 minutes or less, or 100 minutes orless, or 80 minutes or less, or 50 minutes or less. Preferably, thepressure applied within this range is about 2 mm Hg or less, and about0.05 mm Hg or more. It is to be understood that the process describedabove is illustrative of a melt phase process, and that the invention isnot limited to this illustrative process. For example, while referencehas been made to a variety of operating conditions at certain discreteIt.V. values, differing process conditions may be implemented inside oroutside of the stated It.V. values, or the stated operating conditionsmay be applied at It.V. points in the melt other than as stated.Moreover, one may adjust the process conditions based on reaction timeinstead of measuring or predicting the It.V. of the melt. The process isalso not limited to the use of tank reactors in series or parallel or tothe use of different vessels for each zone. Nor is it necessary to splitthe polycondensation reaction into a prepolymer zone and a finishingzone because the polycondensation reaction can take place on a continuumof slight variations in operating conditions over time in onepolycondensation reactor or in a multitude of reactors in series, eitherin a batch, semi-batch, or a continuous process.

In step c) of the process, a stabilizer or a catalyst deactivator isadded to the polymer melt. By a catalyst deactivator is meant a compoundeffective to at least partially deactivate the Sb catalytic activity. Acompound is effective to at least partially deactivate an antimonycatalyst when by its addition at a given level, the rate of AAgeneration upon melting particles or the residual AA level in theperform is reduced relative to the no additive case and/or, solely fortesting the functionality of a compound at a given level, a) when therate of solid-stating is reduced relative to the no additive case, or b)when added earlier, the rate of melt-phase polycondensation is reducedrelative to the no additive case. The stabilizer or catalyst deactivatoris added late during manufacturing to the polymer melt in order to limitthe activity of antimony during subsequent melt processing steps andwhich would otherwise catalyze the conversion of acetaldehyde precursorspresent in the polymer to acetaldehyde. Left untreated, the polymerwould have a high acetaldehyde generation rate during extrusion orinjection molding and would produce an unacceptable amount ofacetaldehyde in the preforms and bottles made from the polymer. Thestabilizer or deactivator can also help thermally stabilize the polymermelt near the end of melt phase polycondensation and during remelting,for example, melt processing into articles, without which more reactionswould occur to cleave the polymer chains in the highly viscous melt.

The stabilizer/deactivator compound is added at any point in the meltphase process after the polymer obtains an It.V. of at least 0.68 dL/gin the most preferably embodiment. In the melt phase, it is preferablyadded at a point when the polymer melt has obtained within +/−0.05 dL/gof the final desired It.V. or the It.V. used for making a preform. Thisis typically at the conclusion of the polycondensation process in thefinisher or after the finisher but prior to pelletization. After thestabilizer/deactivator compound is added, it is recognized that the meltmay continue to polymerize and build up molecular weight to a smallextent, but usually not by more than an additional 0.05 dL/g units. Inany case, the full amount of the stabilizer/deactivator is preferablyadded to the polymer melt before the polymer melt is solidified.

In an ester exchange reaction, a catalyst deactivator can be added atthe conclusion of the ester exchange reaction and beforepolycondensation in molar amounts sufficient to deactivate the esterexchange catalyst without significantly impairing the catalytic activityof the antimony-containing catalyst added after deactivating the esterexchange catalyst. However, the ester exchange catalyst does not have todeactivated prior to adding the antimony-containing catalyst if theester exchange catalyst does not unduly impair the color or thermalstability of the resulting polyester polymer melt phase product.Titanium containing catalysts, however, are preferably deactivated asmuch as possible before the start of polycondensation, and additionalamounts are preferably not thereafter added to the polycondensationzones at all. In the case of direct esterification, and in the absenceof any titanium-containing compounds, stabilizers can be added after thedesired It.V. is obtained.

The stabilizer/deactivator is preferably a phosphorus containingcompound. The phosphorus compound is preferably added to the polymermelt upon reaching an It.V. of at least 0.68 dL/g. The phosphoruscompounds contain one or more phosphorus atoms. Preferred are acidicphosphorus compounds. Acidic phosphorus compounds are defined as havingat least one oxyphosphorus acid group, that is, at least one phosphorusatom double-bonded to one oxygen and single-bonded to at least onehydroxyl or OH group. Specific examples of stabilizers include acidicphosphorus compounds such as phosphoric acid (also known asorthophosphoric acid), pyrophosphoric acid, polyphosphoric acid, andeach of their acidic salts and acidic esters and acidic derivatives,including acidic phosphate esters such as phosphate mono- and di-esters,such as mixtures of mono- and di-esters of phosphoric acid with ethyleneglycol, diethylene glycol, triethylene glycol or 2-ethyl-1-hexanol ormixtures of each; or acidic phosphate esters of pyrophosphoric acid orpolyphosphoric acid with ethylene glycol, diethylene glycol, triethyleneglycol or 2-ethylhexanol, or mixtures of each; or mixtures thereof withor without phosphoric acid, pyrophosphoric acid or polyphosphoric acid.Specific examples of stabilizers that are not acidic phosphoruscompounds include, oligomeric phosphate tri-esters, (tris)ethyleneglycol phosphate, tri-esters of phosphoric acid with ethylene glycol,diethylene glycol, or mixtures of each.

Some types of phosphorus compounds should be avoided in largequantities, and preferably avoided altogether. These types of phosphoruscompounds are those which reduce the antimony catalyst to elementalantimony, that is to the zero oxidation state. Examples of suchphosphorus compounds include phosphorous acid (also known as phosphonicacid) and phosphites. While elemental Sb is useful to provide a level ofreheat capacity to the polymer, greater amounts of elemental Sb thanneeded to reheat the polymer in the shape of a preform are notdesirable. Increasing amounts of elemental antimony grays the polymerand reduces the brightness of the preforms and bottles made from thepolymer. Since the amount of phosphorus compound added tostabilize/deactivate Sb is typically much more than the amount ofphosphorus needed to provide the necessary measure of reheat, phosphoruscompounds which reduce Sb to elemental Sb are desirably used, if at all,in mixture with other non-reducing phosphorus compounds and instoichiometric amounts needed to provide the requisite level of reheatin the preform and no more.

Further, we have discovered that phosphate triesters are not aseffective at stabilizing/deactivating antimony (“Sb”) catalysts as anacidic phosphorus compound such as phosphoric acid.

In some cases, however, a phosphate triester is preferred overphosphoric acid. For example, large quantities of phosphoric acid maypromote corrosion of hoppers, pumps, and reactor vessels if theequipment does not have the proper metallurgy, such as titanium orHastalloy.

The quantity of phosphorus added late relative to the antimony atomsused in this process is not limited, but consideration is taken for theamount of antimony metal and other metals present in the melt. The ratioof phosphorus moles to antimony moles is desirably at least 0.15:1, orat least 0.3:1, or at least 0.5:1, or at least 0.7:1, or at least 1:1,and up to about 3.0:1, preferably up to 2.5:1, or up to 2:1, or up to1.5:1, or up to 1.2:1. The low end of the range is defined by the moreactive additives, that is, acidic phosphorus compounds. When thephosphorus source is a phosphate triester, it may take a phosphorus toantimony mole ratio of at least 0.5:1 to see a significant benefit. Theupper end of the range is defined by 85% phosphoric acid. With thisadditive, a balance must be struck between decreasing AA and decreasingIt.V. From a practical standpoint, It.V. loss has a negative impact onproduction rate. In addition, at some point, the It.V. loss may startinterfering with the AA benefit as a lower It.V. means more hydroxyethylend groups that can react with certain AA precursors to form AA. Asstated earlier, the It.V. loss from late addition of 85% phosphoric acidis greater than that from a neat phosphate triester. Therefore, theupper range for neat phosphate triesters may exceed that stated. It isalso important that the phosphorus level imparted earlier in the processbe kept as low as possible. At the point just prior to late addition ofa phosphorus compound, it is preferred that the phosphorus to antimonymole ratio in the polymer be 0.17:1 or lower. This preference impartsthe maximum AA benefit. A higher phosphorus to antimony mole ratio inthe polymer at the point just prior to late addition of a phosphoruscompound may still result in a lowering of AA; however, the rate ofdecrease in AA with increasing late phosphorus level will be slower andthe maximum decrease in AA will be smaller. That being said, the rangesof phosphorus to antimony mole ratios stated above are formulated in thecase where the phosphorus to antimony mole ratio in the polymerimmediately prior to the late addition of a phosphorus compound was0.17:1 or lower.

Once the desired It.V. is obtained with a minimum It.V. of 0.68 dL/g anda phosphorus compound has been added to the polymer melt tostabilize/deactivate the antimony catalyst, the molten polyester polymerin the melt phase reactors is discharged as a melt phase product andsolidified without the addition of an acetaldehyde scavenger to thepolymer melt. Avoiding the addition of acetaldehyde scavengers isdesirable because acetaldehyde scavengers are costly and can beresponsible for increasing the b* color of the polyester polymer ordecreasing its L* color after toning out yellow, especially when thereaction product of AA and the scavenger is colored. If the AA scavengerhas thermal stability or volatility issues, the effectiveness of a givenamount of scavenger at lowering AA may suffer when the scavenger isadded in the finisher in a polycondensation zone where high heat andhigh vacuum are applied.

An acetaldehyde scavenger is a compound or polymer which interacts byphysical forces or by chemical reaction with acetaldehyde to bindacetaldehyde and prevent its release from the polyester polymer. Ratherthan preventing the formation of acetaldehyde precursors or thesubsequent reactions of the precursors to form AA, the scavengersoperate by binding to acetaldehyde.

Acetaldehyde scavengers are known to those of skill in the art. Examplesinclude polyamides such as those disclosed in U.S. Pat. Nos. U.S. Pat.No. 5,266,413, U.S. Pat. No. 5,258,233 and U.S. Pat. No. 4,8837,115;polyesteramides such as those disclosed in U.S. application Ser. No.595, 460, filed Feb. 5, 1996; nylon-6 and other aliphatic polyamidessuch as those disclosed in Japan Patent Application Sho 62-182065(1987); ethylenediaminetetraacetic acid (U.S. Pat. No. 4,357,461),alkoxylated polyols (U.S. Pat. No. 5,250,333),bis(4-[bgr]-hydroxyethoxyphenyl) sulfone (U.S. Pat. No. 4,330,661),zeolite compounds (U.S. Pat. No. 5,104,965), 5-hydroxyisophthalic acid(U.S. Pat. No. 4,093,593), supercritical carbon dioxide (U.S. Pat. No.5,049,647 and U.S. Pat. No. 4,764,323) and protonic acid catalysts (U.S.Pat. No. 4,447,595 and U.S. Pat. No. 4,424,337), and the most well knownacetaldehyde scavengers are homo and copolyamides such aspoly(caprolactam), poly(hexamethylene-adipamide),poly(m-xylylene-adipamide), and any other compound or polymer having anactive methylene group.

The melt phase product is processed to a desired form, such as amorphousparticles. The shape of the polyester polymer particles is not limited,and can include regular or irregular shaped discrete particles withoutlimitation on their dimensions, including stars, spheres, spheroids,globoids, cylindrically shaped pellets, conventional pellets, pastilles,and any other shape, but particles are distinguished from a sheet, film,preforms, strands or fibers.

The number average weight (not to be confused with the number averagemolecular weight) of the particles is not particularly limited.Desirably, the particles have a number average weight of at least 0.10 gper 100 particles, more preferably greater than 1.0 g per 100 particles,and up to about 100 g per 100 particles.

The method for solidifying the polyester polymer from the melt phaseprocess is not limited. For example, molten polyester polymer from themelt phase may be directed through a die, or merely cut, or bothdirected through a die followed by cutting the molten polymer. A gearpump may be used as the motive force to drive the molten polyesterpolymer through the die. Instead of using a gear pump, the moltenpolyester polymer may be fed into a single or twin screw extruder andextruded through a die, optionally at a temperature of 190° C. or moreat the extruder nozzle. Once through the die, the polyester polymer canbe drawn into strands, contacted with a cool fluid, and cut intopellets, or the polymer can be pelletized at the die head, optionallyunderwater. The polyester polymer melt is optionally filtered to removeparticulates over a designated size before being cut.

Any conventional hot pelletization or dicing method and apparatus can beused, including but not limited to dicing, strand pelletizing and strand(forced conveyance) pelletizing, pastillators, water ring pelletizers,hot face pelletizers, underwater pelletizers and centrifugedpelletizers.

The polyester polymer is one which is crystallizable. The method andapparatus used to crystallize the polyester polymer is not limited, andincludes thermal crystallization in a gas or liquid. The crystallizationmay occur in a mechanically agitated vessel; a fluidized bed; a bedagitated by fluid movement; an un-agitated vessel or pipe; crystallizedin a liquid medium above the T_(g) of the polyester polymer, preferablyat 140° C. to 190° C.; or any other means known in the art. Also, thepolymer may be strain crystallized. The polymer may also be fed to acrystallizer at a polymer temperature below its T_(g) (from the glass),or it may be fed to a crystallizer at a polymer temperature above itsT_(g). For example, molten polymer from the melt phase polymerizationreactor may be fed through a die plate and cut underwater, and thenimmediately fed to an underwater thermal crystallization reactor wherethe polymer is crystallized underwater. Alternatively, the moltenpolymer may be cut, allowed to cool to below its T_(g), and then fed toan underwater thermal crystallization apparatus or any other suitablecrystallization apparatus. Or, the molten polymer may be cut in anyconventional manner, allowed to cool to below its T_(g), optionallystored, and then crystallized.

A preferred solidification technique integrates the cutting with thecrystallization by not allowing the heat energy imparted to the polymerin the melt phase manufacture to drop below the T_(g) before the polymeris both cut and crystallized to at least 20% degree of crystallinity. Inone integrated solidification technique, the molten polyester polymer isdirected through a die, cut at the die plate under water at hightemperature and greater than atmospheric pressure, swept away from thecutter by the hot water and through a series of pipes to provideresidence time to thermally crystallize the particles in the hot liquidwater at a temperature greater than the T_(g) of the polymer andpreferably at about 130 to 180° C., after which the water is. separatedfrom the crystallized particles and the particles are dried. In anotherintegrated solidification technique, the molten polyester polymer is cutunderwater, the particles are immediately separated from the liquidwater after cutting, the particles are dried, and while the particlesare still hot and before the temperature of the particles drops belowthe T_(g) of the polymer and desirably while the particle temperature isabove 140° C., the particles are directed from the dryer onto a surfaceor vessel which allows the particles to form a moving bed with a bedheight sufficient to allow the latent heat within the particles tocrystallize the particles without the external application of a heatingmedium or pressurizing means. Such a surface or vessel is desirably anat least partially enclosed vibrating conveyor, such as is availablefrom Brookman Kreyenborg GmbH.

The degree of crystallinity is optionally at least 30%, or at least 35%,or at least 40%. The melt phase products are preferably substantiallyfree of titanium residues, and in a direct esterification process, arepreferably prepared by adding to the melt phase a polycondensationcatalyst consisting only of antimony containing compound(s). Thus,polyester polymers made in the melt phase having acceptable color can beisolated and provided to a converter without the need for increasingtheir molecular weight in the solid state. By making the high It.V.product in the melt phase, the solid stating step can be altogetheravoided. Solid stating is commonly used for increasing the molecularweight (and the It.V) of the pellets in the solid state, usually by atleast 0.05 It.V. units, and more typically from 0.1 to 0.5 It.V. units.

In addition, certain agents which colorize the polymer can be added tothe melt. In one embodiment, a bluing toner is added to the melt inorder to reduce the b* of the resulting polyester polymer melt phaseproduct. Such bluing agents include blue inorganic and organic toners.In addition, red toners can also be used to adjust the a* color. Organictoners, e.g., blue and red organic toners, such as those tonersdescribed in U.S. Pat. Nos. 5,372,864 and 5,384,377, which areincorporated by reference in their entirety, can be used. The organictoners can be fed as a premix composition. The premix composition may bea neat blend of the red and blue compounds or the composition may bepre-dissolved or slurried in one of the polyester's raw materials, e.g.,ethylene glycol.

Examples of reheat additives (a reheat additive is deemed a compoundadded to the melt in contrast to forming a reheat aid in situ) used incombination with reduced antimony formed in situ or as an alternative toreduced antimony formed in situ include activated carbon, carbon black,antimony metal, tin, copper, silver, gold, palladium, platinum, blackiron oxide, and the like, as well as near infrared absorbing dyes,including, but not limited to those disclosed in U.S. Pat. No. 6,197,851which is incorporated herein by reference.

The iron oxide, which is preferably black, is used in very finelydivided form, e.g., from about 0.01 to about 200 μm, preferably fromabout 0.1 to about 10.0 μm, and most preferably from about 0.2 to about5.0 μm. Suitable forms of black iron oxide include, but are not limitedto magnetite and maghemite. Red iron oxide may also be used. Such oxidesare described, for example, on pages 323-349 of Pigment Handbook, Vol.1, copyright 1973, John Wiley & Sons, Inc.

Other components can be added to the composition of the presentinvention to enhance the performance properties of the polyesterpolymer. For example, crystallization aids, impact modifiers, surfacelubricants, denesting agents, antioxidants, ultraviolet light absorbingagents, colorants, nucleating agents, acetaldehyde bonding compounds,other reheat rate enhancing aids, sticky bottle additives such as talc,and fillers and the like can be included.

The compositions of the present invention optionally may additionallycontain one or more UV absorbing compounds. One example includes UVabsorbing compounds which are covalently bound to the polyester moleculeas either a comonomer, a side group, or an end group. Suitable UVabsorbing compounds are thermally stable at polyester processingtemperatures, absorb in the range of from about 320 nm to about 380 nm,and are difficult to extract or nonextractable from said polymer. The UVabsorbing compounds preferably provide less than about 20%, morepreferably less than about 10%, transmittance of UV light having awavelength of 370 nm through a bottle wall 12 mils (305 microns) thick.Suitable chemically reactive UV absorbing compounds include substitutedmethine compounds of the formula

wherein:

-   -   R is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl,        cycloalkyl, substituted cycloalkyl or alkenyl, or a        polyoxyalkylene chain, such as polyoxyethylene or        polyoxypropylene polymers, each optionally having some        oxypropylene or oxyethylene units in the polymer chain as a        block or random copolymer, the polyoxyalkylene chain having a        number average molecular weight ranging from 500 to 10,000;

R¹ is hydrogen, or a group such as alkyl, aryl, or cycloalkyl, all ofwhich groups may be substituted;

R² is any radical which does not interfere with condensation with thepolyester, such as hydrogen, alkyl, substituted alkyl, allyl, cycloalkylor aryl;

R³ is hydrogen or 1-3 substitutents selected from alkyl, substitutedalkyl, alkoxy, substituted alkoxy and halogen, and

P is cyano, or a group such as carbamyl, aryl, alkylsulfonyl,arylsulfonyl, heterocyclic, alkanoyl, or aroyl, all of which groups maybe substituted.

Preferred methine compounds are those of the above formula wherein: R²is hydrogen, alkyl, aralkyl, cycloalkyl, cyanoalkyl, alkoxyalkyl,hydroxyalkyl or aryl; R is selected from hydrogen; cycloalkyl;cycloalkyl substituted with one or two of alkyl, alkoxy or halogen;phenyl; phenyl substituted with 1-3 substitutents selected from alkyl,alkoxy, halogen, alkanoylamino, or cyano; straight or branched loweralkenyl; straight or branched alkyl and such alkyl substituted with 1-3substitutents selected from the following: halogen; cyano; succinimido;glutarimido; phthalimido; phthalimidino; 2-pyrrolidono; cyclohexyl;phenyl; phenyl substituted with alkyl, alkoxy, halogen, cyano, oralkylsulfamoyl; vinyl-sulfonyl; acrylamido; sulfamyl;benzoylsulfonicimido; alkylsulfonamido; phenylsulfonamido;alkenylcarbonylamino; groups of the formula

where Y is —NH—, —N-alkyl, —O—, —S—, or —CH₂O—; —S—R₁₄; SO₂CH₂CH₂SR₁₄;wherein R₁₄ is alkyl, phenyl, phenyl substituted with halogen, alkyl,alkoxy, alkanoylamino, or cyano, pyridyl, pyrimidinyl, benzoxazolyl,benzimidazolyl, benzothiazolyl; or groups of the formulae

—NHXR₁₆, —CONR₁₅R₁₅, and —SO₂NR₁₅R₁₅;wherein R₁₅ is selected from H, aryl, alkyl, and alkyl substituted withhalogen, phenoxy, aryl, —CN, cycloalkyl, alkylsulfonyl, alkylthio, oralkoxy; X is —CO—, —COO—, or —SO₂—, and R₁₆ is selected from alkyl andalkyl substituted with halogen, phenoxy, aryl, cyano, cycloalkyl,alkylsulfonyl, alkylthio, and alkoxy; and when X is —CO—, R₁₆ also canbe hydrogen, amino, alkenyl, alkylamino, dialkylamino, arylamino, aryl,or furyl; alkoxy; alkoxy substituted with cyano or alkoxy; phenoxy; orphenoxy substituted with 1-3 substitutents selected from alkyl, alkoxy,or halogen substituents; and

P is cyano, carbamyl, N-alkylcarbamyl, N-alkyl-N-arylcarbamyl,N,N-dialkylcarbamyl, N,N-alkylarylcarbamyl, N-arylcarbamyl,N-cyclohexyl-carbamyl, aryl, 2-benzoxazolyl, 2-benzothiazolyl,2-benzimidazolyl, 1,3,4-thiadiazol-2-yl, 1,3,4-oxadiazol-2-yl,alkylsulfonyl, arylsulfonyl or acyl.

In all of the above definitions the alkyl or divalent aliphatic moietiesor portions of the various groups contain from 1-10 carbons, preferably1-6 carbons, straight or branched chain. Preferred UV absorbingcompounds include those where R and R¹ are hydrogen, R³ is hydrogen oralkoxy, R² is alkyl or a substituted alkyl, and P is cyano. In thisembodiment, a preferred class of substituted alkyl is hydroxysubstituted alkyl. A most preferred polyester composition comprises fromabout 10 to about 700 ppm of the reaction residue of the compound

These compounds, their methods of manufacture and incorporation intopolyesters are further disclosed in U.S. Pat. No. 4,617,374 thedisclosure of which is incorporated herein by reference. The UVabsorbing compound(s) may be present in amounts between about 1 to about5,000 ppm by weight, preferably from about 2 ppm to about 1,500 ppm, andmore preferably between about 10 and about 500 ppm by weight. Dimers ofthe UV absorbing compounds may also be used. Mixtures of two or more UVabsorbing compounds may be used. Moreover, because the UV absorbingcompounds are reacted with or copolymerized into the backbone of thepolymer, the resulting polymers display improved processabilityincluding reduced loss of the UV absorbing compound due to plateoutand/or volatilization and the like.

The solid particles produced in the melt phase process preferably havean acetaldehyde generation rate, when measured at 295° C. for 5 minutes,of 20 ppm or less, or 18 ppm or less, or 16 ppm or less. The process ofthe invention does not require melting the particles at 295° C. for 5minutes to make molded articles. The process conditions are notparticularly limited. Compared to the particles that have been made withthe addition of a stabilizer and deactivator in step c) omitted, theparticles produced by this process preferably have a reduction in AAgeneration rate of at least 10% or more, preferably at least 20% ormore, more preferably at least 30% or more, and most preferably of atleast 40% or more. The reduction in AA generation rate is calculated bysubtracting the AA generation rate of the particles with step c) fromthe rate of the particles with step c) omitted and all else being equal,dividing that difference by the rate with step c) omitted, andmultiplying by 100.

In another embodiment, the level of AA in the 20 oz. preform is 11 ppmor less, or 9 ppm or less, or 7 ppm or less, as measured on a preformmolded with a barrel temperature of 285° C. and a residence time of 108seconds.

In yet another embodiment, the free AA on solid particles fed to a meltzone is

10 ppm or less, or 7 ppm or less, or 5 ppm or less, or 3 ppm or less.

The acetaldehyde generation rate can be measured on the solid particlesand the free AA can be measured on solid particles or preforms. Thefollowing method is used to measure acetaldehyde generation on solidparticles.

The method used to determine the level of free AA in the polyesterpolymer composition is the test method ASTM #F2013-00. This test methodis used to measure the level of free acetaldehyde in particles, powders,preforms, bottles, and any other form the polyester polymer compositionmay take. For purposes of measuring residual or free acetaldehyde, thesample is tested according to the method described below. However, forpurposes of measuring the acetaldehyde generation, the sample has toundergo a second melt history in order to determine the level ofacetaldehyde generated. If the sample is a particle or powder which hasnot undergone a melt step in addition to a prior melt phasepolycondensation step, the sample is first treated according to theSample Preparation procedure described below, after which the sample issubmitted to the ASTM #F2013-00 test method for analysis.

The test procedure for measuring the level of free acetaldehyde on asample, whether a preform, pellet, powder, or other form is the ASTM#F2013-00 test method. Samples are cryogenically ground through a WileyMill equipped with a 1.0 mesh screen. The final ground material has a.particle size less than 800 μm. A portion of a sample (0.20 g) isweighed into a 20-mL head-space vial, sealed and then heated at 150° C.for sixty minutes. After heating, the gas above the sealed sample of PETpolymer is injected onto a capillary GC column. The acetaldehyde isseparated, and the ppm of acetaldehyde present in the sample is thencalculated. The amount of acetaldehyde calculated represents the amountof free or residual acetaldehyde present in the sample.

To obtain the acetaldehyde generation rate, the ASTM #F2013-00 testmethod as described above is also used, except that prior to testing thesample by the ASTM #F2013-00 test method, it undergoes a melt history inaddition to the previous melt phase polycondensation. For measuring theacetaldehyde generation rate on preforms, it is sufficient to use thisASTM #F2013-00 Method as described above without subjecting the preformsto a further melt history since by virtue of making a preform, thepellets are melted in an extruder prior to injection molding. By meltextruding or injection molding, AA precursors in the polymer melt havethe opportunity to covert to acetaldehyde. In the event that the sampleis a particle or a powder which has not seen a subsequent melt history,the sample is prepared according the Sample Preparation method, and thensubmitted to the ASTM #F2013-00 test. Sample Preparation: For thepurpose of measuring the acetaldehyde generation rate, and if the samplehas not seen a melt history subsequent to melt phase polycondensation,it is prepared according to this method prior to submitting the sampleto the ASTM #F2013-00 test. Samples of polymer powder ground to pass a 3mm screen are heated in an oven at 115° C. under vacuum (25-30 in. Hg)with a 4 SCFH nitrogen purge for at least 48 h. Although overnightdrying would be sufficient for water removal alone, this extended oventreatment also serves to desorb to about 1 ppm or less the residual AApresent in the high IV powder after melt-phase-only synthesis and priorto AA generation testing. It would take longer to desorb residual AAfrom pellets to about 1 ppm or less, due to the larger particle size(longer diffusion path). Any suitable acetaldehyde devolatizationtechnique can be employed on pellets which reduces the level of freeacetaldehyde down to about 1 ppm or less, including passing hot inertgas over the pellets for a time period sufficient to reduce the residualacetaldehyde to the desired level. The acetaldehyde devolatizationtemperature should not exceed 170° C. The sample is then packed in apreheated Tinius Olsen extrusion plastometer using a steel rod. Theorifice die is calibrated according to ASTM D 1238. A small amount ofmaterial is purged out the bottom, which is then plugged. The piston rodassembly is put in the top of the barrel. A 225 g weight may be placedon top of the piston rod to hold the rod down inside of the barrel. Thepolymer is held at 295° C. for 5 min. The orifice plug is then removedfrom the bottom of the barrel. Via a large weight and operator pressure,the extrudate is pushed out of the barrel into an ice water bath. Theextrudate is patted dry, sealed in a bag and placed in a freezer untilthe ASTM #F2013-00 test is performed.

Alternatively, a CEAST Model 7027 Modular Melt Flow instrument is used.An AA generation program is initiated that will maintain a temperatureof 295° C. and will extrude the melted PET material in 5 minutes at aconstant flow rate as defined in the firmware of the instrument. As theextrudate is pushed out of the barrel and into an ice water bath, thesample is collected, patted dry, sealed in a bag and placed in a freezeruntil the ASTM #F2013-00 test is performed.

Acetaldehyde can be generated in polyester resins with the Ceast Model7027 Modular Melt Flow or any similar extrusion plastometer instrument.The automated functions of this instrument reduce test variability bymaintaining consistent contact times for the polymer inside theextrusion barrel. This particular model of instrument incorporatesautomated packing of the resin at the start of the test procedure. Theinstrument is equipped with a motorized platform that will push thematerial out of the barrel until the piston is at a specified heightabove the bottom of the barrel. The platform will then hold the pistonrod in place, allowing the resin to heat up and generate acetaldehyde.At the end of the specified hold time, the platform extrudes theremainder of the resin out of the barrel while traveling at a constantspeed. These steps eliminate the possibility of variability in resultsfrom packing the material through the final extrusion step. Variabilityin loading the polymer is reduced with the design of the barrel, but isnot automated.

Acetaldehyde can be generated in the above manner over a temperaturerange of 265° C. to 305° C. The most consistent results are obtainedbetween 285° C. and 295° C. The length of time the resin is held insidethe barrel shows good results when between 2 and 15 minutes. The rangeof 5 to 10 minutes shows the best repeatability and distinction betweenmaterials. For the AA generation numbers stated for this invention, 295°C. and 5 minutes were used.

Use of this method of acetaldehyde generation and testing allows forscreening of polyester resins for acetaldehyde generation withoutneeding large amounts of material for evaluations such as molding ofbottle preforms. As little as 10 grams of material may be used in thisprocess making it ideal for testing laboratory samples.

In the invention, it is now possible to provide a feed ofmelt-phase-only synthesis polyester polymer particles to a subsequentmelt processing step (e.g. extrusion/injection molding) having both lowresidual acetaldehyde and a low acetaldehyde generation rate.Advantageously, the melt phase production of the polyester particles nolonger has to be controlled or restricted to the production of polyesterpolymer particles having a low level of residual acetaldehyde. Instead,a polyester polymer particle having a high level of residualacetaldehyde and a low acetaldehyde generation can now be obtained fromthe melt phase production of the polyester polymer. By this method, arobust melt-phase production process with wide processing windows isfeasible in which the addition of an acetaldehyde scavenger is notnecessary or desirable, which allows for the use of a conventional Sbcatalyst composition, and permits the advancement of the polyesterpolymer to a. high It.V. By deactivating the Sb catalyst such that theconversion of acetaldehyde precursors does not occur during subsequentmelt processing, and the post-melt-phase-polycondensation elimination ofresidual acetaldehyde, particles fit for making preforms can be providedto an injection molding machine.

Thus, in another embodiment, once particles are obtained from the meltphase production process, the residual acetaldehyde present in theparticles is reduced by conventional means or by a preferred means asdescribed below. The amount of residual acetaldehyde in the solidparticles is reduced by techniques other that solid state polymerizationprocesses which are expensive and result in significant molecular weightadvancement. Desirably, the residual acetaldehyde in the solid particlesare reduced in the solid state to a level of 10 ppm or less withoutincreasing the It.V. of the particles by more than 0.03 dL/g. In thismore preferred embodiment, the particles are not remelted anddevolatized in order to reduce their level of acetaldehyde, nor are theparticles subjected to solid state polymerization techniques whichresult in advancing the It.V. of the particles more than 0.03 dL/g. Morepreferably, the level of residual acetaldehyde in the solid particles isreduced to a level of 5 ppm or less. Most preferably, the level ofresidual acetaldehyde in the solid particles is reduced to a level of 2ppm or less.

Any conventional technique for reducing the acetaldehyde in theparticles is suitable other than solid state polymerization techniquesand preferably other than by remelting/devolatization. For example, thevacuum procedure described previously as part of the sample preparationfor the AA generation rate test; however, on a larger scale, a vesselwould replace the oven.

Another technique to reduce the level of acetaldehyde in solid particleswithout advancing their molecular weight beyond 0.03 dL/g is referred toherein as acetaldehyde stripping. By this method, the residualacetaldehyde of the particles is reduced by introducing the particlesinto a vessel to form a bed of particles within the vessel, andcontacting the bed with a stream of gas introduced at a gas flow ratenot exceeding 0.15 SCFM per pound of particles per hour, and withdrawingfinished particles from the vessel having a reduced amount of residualacetaldehyde.

In a gas stripping operation, a gas such as air or an inert gas such asnitrogen is contacted with the polyester polymer particles eitherco-current or countercurrent, preferably countercurrent to the flow ofthe particles in a vessel in a continuous or batchwise process,preferably a continuous process. The temperature of the gas introducedinto the AA stripping vessel is not particularly limited, and can rangefrom ambient to 180° C., but preferably from ambient to 70° C., or up toabout 50° C., or up to about 40° C., and more preferably about ambient.The temperature of the gas exiting the stripping vessel will approximatethe temperature of the pellets introduced into the vessel. Thus, ifparticles are introduced at 100° C., the exit temperature of the gaswill be about 100° C.+/−20° C. The temperature of the gas exiting thevessel should not exceed a temperature at which the molecular weight ofthe particles is advanced in the solid state by more than 0.03 dL/g. Theresidence time of the particles depends on the gas temperature andparticle mass/gas ratio, but in general, the residence time ranges from1 hour to 30 hours The gas composition is not particularly limited, andincludes nitrogen, carbon dioxide, or ambient air. The gas does not needto be dried, since the function of the gas is not to dry the pellets butto strip residual AA from the pellets. If desired, however, the gas maybe dried.

While gas stripping of acetaldehyde may also occur in the dryer feedingthe extruder for making an article, it is preferred to feed the dryerwith polymer particles already having 10 ppm or less of residualacetaldehyde in order to reduce the gas flow used in the dryer and/orimprove the quality of the articles made from the extruder. Moreover, inan AA stripping process, dry gas is not required to strip the AA fromthe particles, whereas in a drying process, a stream of dried air iscirculated through the particles primarily to reduce the moisture on orin the particles with the secondary advantage of also removing AA. Thus,in an AA stripping process, ambient air can be and preferably is used asthe stripping medium.

Thus, in one embodiment, the particles of the invention having an It.V.of at least 0.68 dL/g and a degree of crystallinity within a range of20% to 55% and having a residual acetaldehyde level of 10 ppm or moreare fed to a vessel, preferably through the upper end of a vessel, ashot particles (e.g. 100° C. to 180° C.) to increase the efficiency of AAstripping and form a bed of pellets flowing by gravity toward the bottomend of the vessel while a countercurrent flow of gas such as ambient airis circulated through the bed, said gas introduced into the vessel at atemperature ranging from ambient conditions to 70° C., or from ambientto 40° C., to thereby reduce the level of residual AA on the particlesintroduced into the vessel. The particles are withdrawn from the vesselwithin about 5 to 30 hours of their introduction into the countercurrentstream of gas. While the vessel can be pressurized, it is preferably notpressurized except by the pressure created from the gas flow. The vesselis desirably operated at about 0-5 psig, or ambient pressure.

The level of residual acetaldehyde present on the stripped particles is10 ppm or less, or 7 ppm or less, or 5 ppm or less, or 3 ppm or less, or2 ppm or less, or 1.5 ppm or less. The level of residual acetaldehydepresent on the particles fed obtained from the melt phasepolycondensation is generally 10 ppm or more, or 20 ppm or more, or 25ppm or more, or 30 ppm or more. In another embodiment, the difference inthe residual acetaldehyde levels of the pellets entering the strippingvessel and those exiting the vessel is at least 5 ppm, or at least 10ppm, or at least 20 ppm, or at least 30 ppm.

The gas can be introduced into the vessel by any conventional means,such as by a blower, fans, pumps, and the like. The gas may flowco-current to or countercurrent to or across the flow of particlesthrough the vessel. The preferred flow of gas through the bed ofparticles is countercurrent to the particle flow through the bed. Thegas can be introduced at any desired point on the vessel effective tolower the level of acetaldehyde in the particles exiting the vessel ascompared to those fed to the vessel. Preferably, the gas introductionpoint is to the lower half of the bed height in the vessel, and morepreferably to the lower ¼ of the bed height. The gas flows through atleast a portion of the particle bed, preferably through at least 50volume % of the bed, more preferably through at least 75% of theparticle bed volume. Any gas is suitable for use in the invention, suchas air, carbon dioxide, and nitrogen. Some gases are more preferred thanothers due to the ready availability and low cost. For example, the useof air rather than nitrogen would lead to significant operating costimprovements. It was believed that the use of nitrogen gas was requiredin operations which pass a hot flow of gas through a bed of particles attemperatures above 180° C., such as in a preheater or solid-stater,because nitrogen is inert to the oxidative reactions, resulting inpellet discoloration, which would otherwise occur between many polyesterpolymers and the oxygen in ambient air. However, by keeping the processtemperature low such that the gas exiting the vessel does not exceed190° C., particle discoloration is minimized. In one embodiment, the gascontains less than 90 vol % nitrogen, or less than 85 vol % nitrogen, orless than 80 vol % nitrogen. In another embodiment, the gas containsoxygen in an amount of 17.5 vol % or more. The use of air at ambientcomposition (the composition of the air at the plant site on which thevessel is located), or air which is not separated or purified, ispreferred. Desirably, ambient air is fed through the gas inlet. Whilethe air can be dried if desired, it is not necessary to dry the airsince the object is to remove acetaldehyde from the particles.

Any vessel for containing particles and allowing a feed of gas andparticles into and out of the vessel is suitable. For example, there isprovided a vessel having at least an inlet for gas, and inlet for thepolyester polymer particles, an outlet for the gas, and an outlet forthe finished particles. The vessel is preferably insulated to retainheat. The gas inlet and the finished particle outlet are desirablylocated below the gas outlet and the particle inlet, preferably with thegas outlet and particle inlet being toward the top of the vessel and thegas inlet and finished particle outlet being toward the bottom of thevessel. The gas is desirably introduced into the bed within the vesselat about ½ or more desirably at about the lower ¼ of the bed heightwithin the vessel. The particles are preferably introduced at the top ofthe vessel, and move by gravity to the bottom of the vessel, while thegas preferably flows countercurrent to the direction of the particleflow. The particles accumulate within the vessel to form a bed ofparticles, and the particles slowly descend down the length of thevessel by gravity to the finished particle outlet at the bottom of thevessel. The bed height is not limited, but is preferably at asubstantially constant height in a continuous process and is at least75% of the height of the vessel containing the particles within thestripping zone. The vessel preferably has an aspect ratio L/D of atleast 2, or at least 4, or at least 6. While the process can beconducted in a batch or semi batch mode in which as the particles wouldnot flow and the stream of gas can be passed through the bed ofparticles in any direction, the process is preferably continuous inwhich a stream of particles continuously flows from the particle inletto the finished particle outlet as the particles are fed to the vessel.

A suitable gas flow rate introduced into the vessel and passing throughat least a portion of the particle bed is one which is sufficient tolower the amount of residual acetaldehyde on the particles exiting thevessel as compared to those introduced into the vessel. For example, forevery one (1) pound of particles charged to the vessel per hour,suitable gas flow rates introduced into the vessel are at least 0.0001standard cubic feet per minute (SCFM), or at least 0.001 SCFM, or atleast 0.005 SCFM. High flow rates are also suitable, but not necessary,and the gas flow rate should be kept sufficiently low to avoidunnecessary energy consumption by the gas pumps, fans, or blowers.Moreover, it is not desired to unduly cool the particles or dry theparticles because the achievement of either or both of these objectivestypically requires the use of high gas flow rates. The gas flow rate ispreferably not any higher than 0.15 SCFM, or not higher than 0.10 SCFM,or not higher than 0.05 SCFM, or even not higher than 0.01 SCFM forevery one (1) pound of charged particles per hour.

Optimal process conditions to minimize oxidation reactions,discoloration, maintain the It.V. of the particles, and removeacetaldehyde while keeping the production costs low are to introduce thegas at ambient temperature, to feed particles within a range of 150° C.to 170° C. into a vertical cylindrical vessel at an air flow rateranging from 0.002 SCFM to 0.009 SCFM per 1 lb/hr of PET. The size ofthe vessel is such that the residence time of the pellets averages about10 to 24 hours.

The particles of the invention are directly or indirectly packaged as abulk into shipping containers, which are then shipped to customers ordistributors. It is preferred to subject the crystallized particles toany process embodiment described herein without solid state polymerizingthe particles at any point prior to packaging the particles intoshipping containers. With the exception of solid state polymerization,the particles may be subjected to numerous additional processing stepsin-between any of the expressed steps.

Shipping containers are containers used for shipping over land, sea orair. Examples include railcars, semi-tractor trailer containers, Gaylordboxes, ship hulls, or any other container which is used to transportfinished polyester particles to a customer. Customers are typicallyconverter entities who convert the particles into preforms or othermolded articles.

The shipping containers contain a bulk of polyester polymer particles. Abulk occupies a volume of at least 3 cubic meters. In preferredembodiments, the bulk in the shipping container occupies a volume of atleast 5 cubic meters, or at least 10 cubic meters.

In one embodiment, there is provided finished polyester polymerparticles comprising:

-   -   an It.V. of at least 0.68, or 0.70, or 72 dL/g obtained in a        melt phase polymerization production,    -   a degree of crystallinity of at least 20%, preferably at least        30%    -   a residual acetaldehyde level of 10 ppm or less,    -   antimony atoms,    -   phosphorus atoms,

an acetaldehyde generation rate less than 20 ppm, or 18 ppm or less, or16 ppm or less, or a reduction in acetaldehyde generation rate orperform AA of at least 20% or at least 30% or more, relative to thecomposition without the addition of an Sb stabilizer and deactivator,

lacking organic acetaldehyde scavengers, and

which have not been solid state polymerized.

These particles preferably have a b* of 3 or less and an L* of 70 ormore, or 73 or more, or 76 or more, or 79 or more.

By “finished” particles is meant particles that have been subjected bythe particle manufacturer to all the processing conditions needed toproduce a particle ready for feeding into dryer hoppers associated witha molding machine or directly to a molding machine used for convertingparticles into articles, without any further processing steps performedby the particle manufacturer.

If desired, an acetaldehyde scavenger in the form of a solid may becombined as a solid/solid blend with the polyester particles obtainedfrom the melt phase. The acetaldehyde scavenger solids can be combinedwith the polyester polymer pellets prior to their introduction to asubsequent melt processing zone. Alternatively, the acetaldehydescavenger solids can be separately fed to a melt processing zone formaking the article along with a separate feed of the polyesterparticles. The acetaldehyde scavenger solids may be in the form of neatscavengers or in the form of a concentrate of acetaldehyde scavenger ina polyester solid, wherein the concentration of the acetaldehydescavenger in the concentrate ranges from about 0.5 wt. % to 50 wt. %.

The articles can be formed from the melt phase products by anyconventional techniques known to those of skill. For example, melt phaseproducts, optionally solid state polymerized, which are crystallized toa degree of crystallization of at least 20%, are fed to a machine formelt extruding and injection molding the melt into shapes such aspreforms suitable for stretch blow molding into beverage or foodcontainers, or rather than injection molding, merely extruding intoother forms such as sheet. Suitable processes for forming the articlesare known and include extrusion, extrusion blow molding, melt casting,injection molding, a melt to mold process, stretch blow molding (SBM),thermoforming, and the like.

Examples of the kinds of shaped articles which can be formed from themelt phase products and the polyester polymer composition of theinvention include sheet; film; packaging and containers such aspreforms, bottles, jars, and trays; rods; tubes; lids; and filaments andfibers. Beverage bottles made from polyethylene terephthalate suitablefor holding water or carbonated beverages, and heat-set beverage bottlessuitable for holding beverages which are hot filled into the bottles areexamples of the types of bottles which are made from the crystallizedpellet of the invention. Examples of trays are those which are dualovenable and other CPET trays.

In another embodiment of the invention, there is provided a process formaking articles comprising:

-   -   (i) introducing solid polyester polymer particles, having:        -   an It.V. of at least 0.68 dL/g obtained in melt phase            polymerization,        -   a degree of crystallinity of at least 20%,        -   a residual acetaldehyde level of 10 ppm or less,        -   residues of a polycondensation catalyst composition            comprising antimony species,        -   an acetaldehyde generation rate at 295° C. for 5 min. of            less than 20 ppm or 18 ppm or less, or 16 ppm or less,        -   or a reduction in acetaldehyde generation rate or perform AA            of at least 20% or at least 30%, relative to the composition            without the addition of an Sb stabilizer and deactivator,        -   and lacking organic acetaldehyde scavengers,    -   into a melt processing zone and melting the particles to form a        molten polyester polymer composition; and    -   (ii) forming an article comprising a sheet, strand, fiber, or a        molded part from the molten polymer composition.

In this embodiment, Sb catalyzed polyester polymer particles produced inthe melt phase are made to a high It.V. and are provided as a suitablefeed to the melt processing zone by having both low residualacetaldehyde and a low acetaldehyde generation rate without the presenceof acetaldehyde scavengers in the particles fed to the melt processingzone. In this case, the acetaldehyde generation is measured on theparticle feed, using the Sample Preparation technique described above toimpart a melt history to the particles. In this embodiment, the residualacetaldehyde can be lowered to less than 10 ppm acetaldehyde by gasstripping the particles produced from the melt phase production process.Further, the catalyst stabilizer/deactivator added in the melt phaseinhibits the Sb catalyst residues in the polymer from convertingacetaldehyde precursors to acetaldehyde. In this embodiment, theparticles fed to the melt processing zone are preferably not solid-statepolymerized. The polyester particles made by melt-phase-only synthesishave a small surface to center molecular weight gradient and undergoless It.V. loss during melt processing than conventional polyesters. Forexample, bottles and/or preforms, and in particular beverage bottlessuch as carbonated soft drink or water bottles are made from theparticles of the invention and the It.V. difference between the It.V. ofthe particles and the It.V of the preforms and/or bottles is not morethan 0.04 dL/g, preferably not more than 0.03 dL/g, and most preferablynot more than 0.02 dL/g.

In another embodiment, the molded article preferably lacks an organicacetaldehyde scavenger. Preferably, ingredients added to the solidpolyester particles at the melt processing step do not include organicacetaldehyde scavengers.

In another embodiment, there is provided a process for making articlescomprising:

-   -   (i) introducing solid polyester polymer particles, having:        -   an It.V. of at least 0.68 dL/g obtained in melt phase            polymerization,        -   a degree of crystallinity of at least 20%,        -   a residual acetaldehyde level of 10 ppm or less, residues of            a polycondensation catalyst composition comprising antimony            species, and        -   lacking acetaldehyde scavengers,    -   into a melt processing zone and melting the particles to form a        molten polyester polymer composition; and    -   (ii) forming an article comprising a sheet, strand, fiber, or a        molded part from the molten polymer composition, wherein the        article, such as a perform or bottle, has less than or equal to        about 10 ppm of acetaldehyde, or 8 ppm or less acetaldehyde.

The amount of AA on the molded article can be measured by ASTM F2013-00,using an injection molding temperature setting of 285° C. and the meltresidence time of about 108 seconds. Alternatively, preforms made fromthe particles of this invention have a reduction in perform AA of atleast 20% or at least 30% or more, relative to preforms made from thecomposition without the addition of an Sb stabilizer and deactivator.

In this embodiment, the level of residual acetaldehyde is measured onthe article, such as on a preform. In this case, a heat history need notbe imparted to the preform sample since the particles were remelted inthe injection molding machine. The amount of residual acetaldehydepresent in the particles after drying but prior to injection moldingshould be subtracted from the residual acetaldehyde value obtained inthe perform.

At the melt processing extruder, other components can be added to theextruder to enhance the performance properties of the pellets. Thesecomponents may be added neat to the bulk polyester pellets or in aliquid carrier or can be added to the bulk polyester pellets as a solidpolyester concentrate containing at least about 0.5 wt. % of thecomponent in the polyester polymer let down into the bulk polyester. Thetypes of suitable components include crystallization aids, impactmodifiers, surface lubricants, denesting agents, compounds,antioxidants, ultraviolet light absorbing agents, colorants, nucleatingagents, reheat rate enhancing aids, sticky bottle additives such astalc, and fillers and the like can be included. All of these additivesand many others and their use are well known in the art and do notrequire extensive discussion.

In yet another embodiment, since the amorphous particles produced in themelt phase polymerization process are preferably crystallized but notsolid state polymerized, the phosphorus compound may optionally also beadded to polyester polymer particles by either melt compounding thephosphorus compounds with the polyester polymer particles to form asolid concentrate of polyester polymer particles containing randomlydispersed phosphorus compounds, after which the concentrate is fed tothe melt processing zone for making an article along with a feed streamof polyester particles; or a stream of phosphorus compounds can be addeddirectly to the melt processing zone to make the articles as a neatstream or in a slurry or dispersion, together with a stream of thepolyester polymer particles.

The bottle preforms made from the polyester polymer obtained by theprocess of the invention will have an L* of at least 50, or at least 60,or at least 65, or at least 70. Further, the bottle preforms made fromthe polyester polymer obtained by the process of the invention will havea b* value of no greater than 3.0, while maintaining an L* brightness ofat least 50, or at least 60, or at least 65, or at least 70.

Although Sb-catalyzed polyesters that are solid-stated have lower AAgeneration rates than those built up virtually exclusively in the meltphase, there is still room for improvement in AA generation rate of thesolid-stated pellets, especially for applications like water bottles. Inanother embodiment, solid-stated pellets are melt blended with an acidicphosphorus compound in an extruder or static mixer or some other mixingdevice. The AA generation rate of the solid-stated polymer treated withthe acidic phosphorus compound is lower than the same solid-stated resinput through the same mixing process but with no additive.

The mixing device where the acidic phosphorus compound is introduced maybe part of the injection molding process, or it may be a separate stepprior to injection molding. The acidic phosphorus compound may beintroduced neat, in a liquid carrier or via a polymer concentrate.Introduction neat or in a liquid carrier is more preferred sincereaction with the catalyst in the polymer carrier may lowereffectiveness. If acidic phosphorus compound is a liquid and is addedneat, a mixer at ambient conditions could be used to coat the pelletswith the liquid additive prior to entry into an extruder. If the polymerconcentrate route is used, the concentrate pellets could be dry blendedat ambient conditions with the solid-stated pellets to make a ‘salt andpepper’ type blend. These same comments and approaches apply to meltblending an acidic phosphorus compound with pellets made exclusively inthe melt-phase.

The quantity of phosphorus added late relative to the antimony atomsused in this process is not limited, but consideration is taken for theamount of antimony metal and other metals present in the melt. The ratioof phosphorus moles to antimony moles is desirably at least 0.15:1, orat least 0.3:1, or at least 0.5:1, or at least 0.7:1, or at least 1:1,and up to about 3.0:1, preferably up to 2.5:1, or up to 2:1, or up to1.5:1, or up to 1.2:1

Reaction between acidic phosphorus compounds and Sb catalyst are fastper Example 8. The AA generation results are similar for a meltresidence time of about 1 minute and that of about 3.3 minutes. Sincethe time is short in a melt-blending process, acidic phosphoruscompounds are preferred over phosphate triesters, which react moreslowly.

Examples 5, 6 & 8 illustrate the lower AA generation rate and lowerresidual AA of this embodiment. The solid-stated polyester used in theseexamples worked well because the phosphorus level in the pellets was lowprior to melt blending. At the point just prior to late addition of aphosphorus compound, it is preferred that the phosphorus to antimonymole ratio in the polymer be 0.17:1 or lower. In fact, it is notrequired that the solid-stated pellets contain any phosphorus prior tomixing with the acidic phosphorus compound. This preference for a P:Sbmole ratio of 0.17 or lower imparts the maximum AA benefit. A higherphosphorus to antimony mole ratio in the polymer at the point just priorto late addition of a phosphorus compound may still result in a loweringof AA; however, the rate of decrease in AA with increasing latephosphorus level will be slower and the maximum decrease in AA will besmaller. These comments on low P levels in pellets also apply to blendswith polyester pellets made exclusively in the melt-phase.

In addition to lowering AA generation rate, melt-blending of phosphoruslowers the solid-stating rate. Slower solid-stating rates support themechanism of partial catalyst deactivation. The extent of the decreasein solid-stating rate will depend on the P:Sb mole ratio, where thedecrease in rate will be larger as mole ratio increase. The samplewithout H3PO4 took about 1.6 hours to reach 0.76 IhV while the samplewith 90 ppm P from H3PO4 took about 8 hours to reach 0.76 IhV.

This invention can be further illustrated by the additional examples ofembodiments thereof, although it will be understood that these examplesare included merely for purposes of illustration and are not intended tolimit the scope of the invention.

EXAMPLES

Most of the high IV polyesters in the examples of the invention weremade exclusively in the melt phase, i.e., the molecular weight of thepolyester melt-phase products as indicated by their IhV or ItV were notincreased in the solid state. Exceptions are the examples involvingaddition of the stabilizing/deactivating compound during the meltprocessing step such as Examples 5, 6, & 8, in which commercial PET thathad been solid-stated was used to feed the melt processing step.

A commercial polyester sold to make carbonated soft drink bottles asCB-12 available from Eastman Chemical Company is submitted every timethe AA generation test is done on experimental samples. The AA level inpreforms made from CB-12, a polymer made under typical processingconditions and solid-state polymerized, is considered acceptable. The AAgeneration results on this commercial polyester are considered as abenchmark: AA generation rates less than or equal to the AA generationvalue of the commercial CB-12 pellets indicate an acceptable level ofpreform AA for carbonated soft drink applications at the time thetesting is done

Comparative Example 1

The starting oligomeric mixture employed in the polycondensations wasprepared from terephthalic acid, ethylene glycol, about 1.4 mole percentof about 35% cis/65% trans 1,4-cyclohexanedimethanol, and about 2.7 molepercent of diethylene glycol generated during esterification. Theconversion of acid groups was about 93.5% by titration methods alone and92.9 to 95.9% by NMR/titration carboxyl ends groups methods. The M_(n)of the oligomeric mixture was about 843 g/mole, and the M_(w) was about1928 g/mole.

For polycondensation, the ground oligomer (103 g) is weighed into ahalf-liter, single-necked, round-bottomed flask. The catalyst solutionadded to the flask is antimony triacetate in ethylene glycol. A 316 Lstainless steel paddle stirrer and glass polymer head were attached tothe flask. After attaching the polymer head to a side arm and a purgehose, two nitrogen purges are completed.

The polymerization reactor is operated under control of a CAMILE™automation system, programmed to implement the following array.

Stir Time Temp. Vacuum Speed Stage (min.) C.° (torr) (rpm) 1   0.1 285730  0 2 10 285 730  150* 3  2 285  140*  300* 4  1 285 140 300 5 10 285 51* 300 6  5 285  51 300 7  1 285    4.5* 300 8 20 285    4.5 300 9  2285    0.8*  30* 10 500# 285    0.8  30 *= ramp; #= torque termination

A molten bath of Belmont metal is raised to surround the flask, and theCAMILE™ array is implemented. In this array, a “ramp” is defined as alinear change of vacuum, temperature, or stir speed during the specifiedstage time. The stirring system is automatically calibrated betweenstages 4 and 5. The finisher stage (10) is terminated according to thestirrer torque. The average reaction time is about 58 min.; therefore,this will be the finisher time used in the following example. Thepolymer is cooled for about 15 min., separated from the glass flask,cooled for about 10 min. and placed immediately into liquid nitrogen.The polymers are ground cryogenically to pass a 3 mm screen. Theresidual or free AA sample is kept frozen.

Table 1 sets forth the analytical results. The measurement techniquesfor determining free AA, AA generation, L* and b* were as described asabove. L* and b* were measured on the powder.

TABLE 1 AA Finisher XRF AA Gen Time Sb XRF P IhV ItV L* b* Free 295/5Sample # (min) (ppm) (ppm) (dL/g) (dL/g) Color Color (ppm) (ppm) 5660.67 239 2 0.761 0.802 78.81 4.37 22.79 26.42 58 54.78 242 2 0.7620.803 80.43 4.52 22.48 25.96 CB-12 . . . . . . . 1.06 20.08

In the Table 1 runs, no phosphorus compound was added. From the resultsin Table 1, it can be seen that Sb-catalyzed, high IV melt-phase PETpolyesters have higher free AA and a higher AA generation rate than thecommercial, solid-stated PET (CB-12).

Example 2

In this example, the phosphorus stabilizer is added during the meltphase manufacturing step. The oligomers described in Example 1 were usedin this example. Phosphorus thermal stabilizers are added to polyesterpolymers. When terminating a polymer run at a torque equivalent toapproximately 0.80 IhV, the reaction time was about 58 min, perExample 1. After the 58 minutes of polymerization time, the vacuum wasbroken, the phosphorus compound was added, and vacuum was resumed toenhance mixing.

In this example, the phosphorus compound is either phosphoric acid or anoligomeric phosphate triester (OPT). To minimize the potential loss inItV, a concentrated form of the phosphorus compound was used. By using aconcentrated form of the phosphorus compound, the amount of solventpresent which could hydrolyze or glycolyze the polymer is reduced.Phosphoric acid was added as an 85 weight % solution in water.Oligomeric phosphate tri-esters were added directly as a 9 wt./wt. %phosphorus solution.

The following array sets forth the processing conditions for runs withlate addition of a phosphorus compound. The phosphorus compounds wereadded at stage 12. For each phosphorus target, two polymer runs weremade per the following array, one for the addition of phosphoric acid,and one for the addition of oligomeric phosphate triesters.

Time Temperature Vacuum Stir Speed Stage Minutes C.° torr rpm 1 0.1 285730  0 2 10 285 730  150* 3 2 285  140*  300* 4 1 285 140 300 5 10 285 51* 300 6 5 285  51 300 7 1 285    4.5* 300 8 20 285    4.5 300 9 2 285   0.8*  30* 10 58 285    0.8  30 11 3 285  650*  30 12 2 285 650  30 131 285    0.5*  45* 14 5 285    0.5  45 *= ramp

Table 2 sets forth the analytical results.

TABLE 2 % % Reduction XRF P:Sb Free Reduction AA Gen in Sb XRF P Mole L*b* AA in Free 295/5 AA Smp # Additive ppm ppm Ratio IhV ItV Color Color(ppm) AA** (ppm) Gen** CB- 1.06 20.08 12 70 None 243 2 0 0.84 0.89176.44 4.6 22.08 3.5 25.3 1.2 71 None 243 1 0 0.83 0.88 79.7 4.44 24.74−8.2 25.76 −0.6 64 n.d.* 244 3 0 0.833 0.883 79.09 5.41 21.79 4.7 25.73−0.5 61 H₃PO₄ 247 93 1.5 0.808 0.855 77.39 4.28 14.97 34.5 15.1 41.0 66H₃PO₄ 243 129 2.1 0.751 0.791 78.83 3.94 10.59 53.7 17 33.6 67 OPT 24634 0.5 0.843 0.894 78.79 3.9 21.46 6.2 24.88 2.8 65 OPT 246 67 1.1 0.8140.862 80.26 4.08 20.09 12.2 16.47 35.7 63 OPT 246 109 1.7 0.799 0.84580.35 4.42 17.89 21.8 22.1 13.7 *n.d. = none detected: this row hasphosphoric acid (H₃PO₄) added late at the lowest target (40 ppm P) and,according to XRF testing, does not contain the phosphorus expected:therefore, the flask walls or stirrer rod may have received the verysmall amount of H₃PO₄, or the very small amount was just too difficultto measure and/or deliver. **When there is more than one run without P,the AA values for the runs without P are averaged prior to use in thiscalculation. A negative reduction indicates an increase in AA.

As can be seen from Table 2, both phosphoric acid (H₃PO₄) and theoligomeric phosphate triester (OPT) lower free AA and AA generationrates. At high phosphorus levels, phosphoric acid was more effective atreducing the AA generation rate than OPT. Retaining the flexibility oflowering the AA generation rate at higher phosphorus levels is desirableto ensure that the catalyst is sufficiently stabilized/deactivated. Thephosphorus level chosen is a balance between the % reduction needed inAA generation rate and the It.V. loss incurred

Comparative Example 3

The starting oligomeric mixture employed in the polymerizations orpolycondensations was prepared from terephthalic acid, ethylene glycol,about 1.2 mole percent of about 35% cis/65% trans1,4-cyclohexanedimethanol, and about 2.8 mole percent of diethyleneglycol generated during esterification. The conversion of acid groupswas about 94.5% by titration methods alone and 94.6% by NMR/titrationcarboxyl ends groups methods.

The procedure and Camile array described in Example 1 were used here aswell. Table 3 sets forth the analytical results.

TABLE 3 Finisher Sam- Time XRF IhV ItV L* b* ple (min) Sb XRF P (dL/(dL/ Color Color # (min) (ppm) (ppm) g) g) CIELAB CIELAB 1 77 235 10.788 0.832 79.7 3.41 2 84 238 1 0.807 0.854 78.78 2.88 6 67 240 2 0.7830.827 81.58 4.13 8 92 233 1 0.821 0.87 78.35 4.97

The average reaction time is about 80 min.; therefore, this will be thefinisher time used in the following example.

Example 4

In this example, the phosphorus stabilizer is added during the meltphase manufacturing step. The oligomers described in Example 3 were usedhere as well. Phosphorus thermal stabilizers are added to polyesterpolymers. When terminating a polymer run at a torque equivalent toapproximately a 0.80 IhV, the reaction time was about 80 min, perExample 3. After the 80 minutes of polymerization time, the vacuum wasbroken, the phosphorus compound was added, and vacuum was resumed toenhance mixing. The procedure and array described in Example 2 were usedhere except for the stage 10 time. Table 4 sets forth the analyticalresults.

TABLE 4 % Reduction AA XRF P:Sb Free in Gen % Reduction Sb XRF P MoleIhV ItV L* b* AA Free 295/5 in AA Sample # Additive (ppm) (ppm) Ratio(dL/g) (dL/g) Color Color (ppm) AA (ppm) Gen CB-12 0.7 20.73 10 None 2431 0.0 0.855 0.908 78.22 3.96 29.55 −2.9 28.65 −8.0 28 None 239 2 0.00.835 0.885 76.94 3.52 29.02 −1.0 23.78 10.3 46 None 237 2 0.0 0.8390.89 77.14 2.83 27.6 3.9 27.13 −2.3 34 H3PO4 236 65 1.1 0.779 0.82276.03 2.93 16.89 41.2 19.39 26.9 20 H3PO4 239 85 1.4 0.844 0.896 74.743.52 20.42 28.9 15.45 41.7 42 H3PO4 241 95 1.5 0.805 0.852 77.86 2.5914.37 50.0 17.03 35.8 30 H3PO4 243 103 1.7 0.784 0.828 75.85 5.25 15.2746.8 16.85 36.5 24 H3PO4 232 133 2.3 0.769 0.811 77.53 3.68 14.48 49.617 35.9 38 H3PO4 236 146 2.4 0.8 0.846 79.92 5.93 14.38 49.9 14.04 47.622 OPT 234 21 0.4 0.826 0.875 77.39 3.04 17.17 40.2 22.32 15.8 40 OPT225 61 1.1 0.808 0.855 79.1 3.01 21.61 24.8 21.18 20.1 26 OPT 238 65 1.10.812 0.859 77.81 2.85 21.49 25.2 22.68 14.5 44 OPT 237 93 1.5 0.7960.841 78.12 2.91 17.94 37.5 14.99 43.5 36 OPT 238 96 1.6 0.821 0.8779.12 2.59 21.54 25.0 22.18 16.4 32 OPT 241 130 2.1 0.799 0.845 77.264.35 14.65 49.0 19.34 27.1

The additional data in Table 4 confirm the preliminary data of Table 2.As can be seen from Table 4, both phosphoric acid (H₃PO₄) and theoligomeric phosphate triester (OPT) lower free AA and AA generationrates. At high and low phosphorus levels, phosphoric acid was moreeffective at reducing the AA generation rate than OPT. Retaining theflexibility of lowering the AA generation rate at high phosphorus levelsis desirable to ensure that the catalyst is sufficientlystabilized/deactivated. The phosphorus level chosen is a balance betweenthe % reduction needed in AA generation rate and the It.V. lossincurred.

The free AA of sample 20 was lowered. Five grams of the sample wereplaced in a 115° C. oven under full vacuum (about 29 in. Hg) for about48.5 hours. The sample was placed in a desiccator to cool for 30 min.and then was frozen until tested.

Free AA Sample # Additive Treatment (ppm) CB-12 None 0.74 20 H3PO4 None7.18 20 H3PO4 Oven 0.97Time had passed after sample #20 was made, ground and stored at ambientconditions; therefore, the free AA in the untreated sample was lowerthan the original measurement due to normal attrition of a volatilecompound. The oven treatment lowered the free AA in Sample #20 to about1 ppm.

Example 5

In this example, the phosphorus stabilizer is added during the meltprocessing step (melting a solid polyester polymer). A commercial PETwas modified with 1.5 mole percent of about 35% cis/65% trans1,4-cyclohexanedimethanol, and about 2.8 mole percent of diethyleneglycol. It contained about 250 ppm Sb and about 8 ppm P. The PET wasdried overnight at 120° C. in an air dryer with desiccant beds. Asbefore, the phosphorus compound is either phosphoric acid or anoligomeric phosphate triester (OPT). 4500 grams of PET pellets weremixed with the liquid phosphorus compound in a Henschel mixer for about30 seconds. The pellets coated with the phosphorus compound were thenfed to a single screw extruder with a barrel temperature of 275° C. anda screw speed of 20 rpm, which was calculated to give a melt residencetime of about 3.3 minutes. The extruded strands were passed through awater bath and pelletized. Free AA samples were stored immediately ondry ice and then transported to a freezer. CB-12 control was notextruded.

Table 5 sets forth the analytical results.

TABLE 5 AA Mixed XRF XRF Free Gen Sample & IhV ItV Sb P L* b* AA 295/5 #Additive Extruded (dL/g) (dL/g) (ppm) (ppm) Color Color (ppm) (ppm)147-4 none No 0.75 0.79 248 8 83.62 −1.76 0.32 16.195 147-1 none Yes0.676 0.708 250 8 61.49 0.81 12.18 21 147-2 OPT Yes 0.645 0.674 246 9759.22 0.41 14.34 17.39 147-3 H₃PO₄ Yes 0.647 0.676 243 107 59.20 0.0911.72 10.8 CB-12 0.75 17.57

In Table 5, the first control is the starting pellets, which have notbeen through the extruder. Per the results of Table 5, H₃PO₄ is muchmore effective at lowering both types of AA than OPT, especially atshort residence times.

Example 6

Melt blending a preformed polymer with an additive in a glass flaskachieves a uniform distribution of additive within the polymer like anextruder would-only with less shear and more time. The same commercialpolymer described in Example 5 is used in this example. The pellets areground to pass a 2 mm screen, and 100 grams of the polyester powder areweighed into a 500 mL round bottom flask. The powder is dried at 120° C.under full vacuum (25-30 in. Hg) overnight (about 16 hours) in a vacuumoven. After cooling the flask to room temperature in a desiccator, thecatalyst-deactivating additive or stabilizer is weighed into the flask.The additive is phosphoric acid (H₃PO₄). A polymer head with stirrer isattached and the flask purged twice with nitrogen. A molten bath ofBelmont metal is raised to surround the flask, and the following CAMILE™array is implemented.

Time Temp. Vac Stir Stage Min. ° C. Torr RPM 1 .1 270 730 0 2 5 270 7300 3 5 270 730 0 4 5 270 730 15* 5 4 270 730 35* 6 2 270 730 75* 7 5 270730 75  *= ramp

A moderate nitrogen purge was employed at all times. During Stages 2 &3, the stirrer is turned slowly by hand. Following the end of the array,the polymer is cooled for about 15 min., separated from the glass flask,cooled for about 10 min. and placed immediately into liquid nitrogen.The polymers are ground cryogenically to pass a 3 mm screen. Theresidual or free AA sample is kept frozen. Table 6 sets forth theanalytical results, which will be compared to Example 7.

TABLE 6 XRF AA Sample Sb XRF P IhV ItV Free AA gen L* b* # Additive(ppm) (ppm) (dL/g) (dL/g) (ppm) 295/5 (ppm) Color Color 11 none 201 120.763 0.8 11.58 21.87 84.28 0.34 14 H₃PO₄ 199 92 0.729 0.76 7.85 13.0184.17 0.07 CB-12 0.84 22.63

Example 7

The same oligomeric mixture as described in Example 1 was used herealso. Runs were catalyzed by about 250 ppm Sb. Blue and red organictoners are added. The CAMILE array described in Example 2 is used inthis example as well. Phosphoric acid is added in stage 12. Table 7 setsforth the analytical results.

TABLE 7 Free AA Gen Red Toner Blue Toner XRF P ItV AA 295/5 L* b* Cat.(ppm) (ppm) (ppm) (dL/g) (ppm) (ppm) Color Color Sb 6.29 12.58 87 0.84814.51 11.54 74.3 −2.9 CB-12 0.84 18.64

Example 8

The same polyester and procedure used in Example 5 is used here exceptfor the drying conditions. First, the PET was dried overnight at 150°C., and then the dryers were turned down to 60° C. at 6 AM; however, thePET still had at least about 150 ppm water. The dryers were turned up to150° C. for most of the working day, the water level was down to about50 ppm, and the dryers were turned down to 60° C. overnight. Since thewater level was about 170 ppm in the morning, the PET was moved to adifferent set of dryers and dried at 165° C. for about an hour and ahalf before turning the set-point down to 60° C.

Sample numbers ending with a B &/or C indicate that the single extrusiondenoted by the number portion has multiple samples isolated. The samplewithout a letter is the first cut. The second cut is labeled “B.” Secondand third samples that were not differentiated were labeled “BC.” Thefirst number denotes the number assigned to the extrusion; after aslash, the second # indicates the number under which analytical testingwas submitted. Free AA was only tested once per extrusion. The first rowdescribes the sample taken from the drier immediately prior to extrusion(this sample was not extruded).

In this example, the time in the extruder is varied. The table isarranged with the fast screw speeds or shortest times first within anadditive group. In addition to extrusions with an oligomeric phosphatetriester coated pellets and phosphoric acid coated pellets, there areextrusions with polyphosphoric acid coated pellets and water coatedpellets. The weight of water used was 15% of the weight of the 85%phosphoric acid used, i.e., the amount of water expected to be in theextrusions of pellets coated with 85% phosphoric acid.

TABLE 8 AA Screw XRF Old Free Gen Speed Approx_Time IhV ItV Sb XRF P OldL* b* AA 295/5 Sample # Additive (rpm) (min) (dL/g) (dL/g) (ppm) (ppmColor Color (ppm) (ppm) Dried none 0 0 0.761 0.802 248 8 81.14 −1.980.24 18.61  2 none 80 1 0.711 0.747 250 8 57.9 1.22 5.49 22.54 17 none80 1 0.692 0.726 240 8 56.44 0.44 3.1 21.77  3 none 35 2.1 0.681 0.714251 9 60.03 1.46 9.35 24.07 18 none 35 2.1 0.689 0.722 240 8 59.96 0.8624.15 18B/21 none 35 2.1 0.663 0.694 237 8 58.93 0.66 5.74 21.39  1 none20 3.3 0.672 0.704 250 11 61.02 2.22 22.58 29.5 16 none 20 3.3 0.6810.714 236 8 60.19 1.11 12.04 29.06  4 OPT 80 1 0.627 0.654 247 158 58.281.54 10.36 22.3  5 OPT 35 2.1 0.622 0.649 249 167 60.1 1.09 14.42 22.89 6 OPT 20 3.3 0.624 0.651 235 159 61.06 1.11 21.67 24.49  9 PPA 80 10.665 0.696 240 132 52.83 2.46 11.15  9B/19 PPA 80 1 0.634 0.662 240 13253.35 2.29 10.15 13.71  7 PPA 35 2.1 0.672 0.704 237 125 57.24 1.1411.48 12.65  8 PPA 20 3.3 0.666 0.697 238 130 58.32 1.66 15.52 12.38 11H3PO4 80 1 0.687 0.72 238 97 55.39 0.13 9.12 10.46 12 H3PO4 35 2.1 0.6480.677 238 99 58.75 0.64 10.42 12BC1/23 H3PO4 35 2.1 0.673 0.705 248 10559.63 0.41 10.46 10.67 12BC2/24 H3PO4 35 2.1 0.657 0.687 230 94 59.550.3 10.16 11.1 10 H3PO4 20 3.3 0.634 0.662 234 97 59.83 0.79 13.37 11.4313 water 80 1 0.722 0.759 233 11 57.97 0.72 2.87 18.47 14 water 35 2.10.706 0.741 240 9 59.21 1.11 6.21 22.73 15 water 20 3.3 0.672 0.704 2408 60.16 1.31 27.79 15B/20 water 20 3.3 0.685 0.718 227 8 61.3 1.16 11.8525.13 CB-12 1^(st) 0 0 0.797 0.843 0.77 22.12 CB-12 0 0 0.788 0.832 0.7922.32 last

Per the controls with additive equal none, increasing the residence timein the extruder increases the IV loss, the free AA and the AA generationrate. The pellet size increases with decreasing time in the extruder.The brightness of the polymer increases as the residence time increases.

These extrusions indicate that the reaction between acidic phosphoruscompounds and the antimony catalyst are fast. The AA generation resultsare about the same for a one minute extrusion and a 3.3 minuteextrusion. Phosphoric acid is the best additive in terms of reducing AAgeneration rate and maintaining a bright and neutral color. Whilepolyphosphoric acid reduces AA generation rate almost as well asphosphoric acid, polyphosphoric acid addition makes the PET darker andmore yellow than phosphoric acid addition.

The oligomeric phosphate triester (OPT) reduces the AA generation ratesomewhat at longer extrusion times; however, it is not as effective asacidic phosphorus compounds. There is more IV loss and more reduction inAA generation rate for 85% phosphoric acid than for the 15% water alone.

Example 9

The starting oligomeric mixture employed in the polycondensations wasprepared from terephthalic acid, ethylene glycol, about 2.8 mole:percent of about 35% cis/65% trans 1,4-cyclohexanedimethanol, and about2.8 mole percent of diethylene glycol generated during esterification.The conversion of acid groups was about 93.7% by NMR alone and 94.8% byNMR/titration carboxyl ends groups methods. The M_(n) of the oligomericmixture was about 768 g/mole, and the M, was about 1950 g/mole.

The array used is similar to that shown in Example 2 except thetemperature in all the stages is 275° C. and stage 10 time is 121.2minutes. The “TBP” in Table 9 stands for tributyl phosphate, and thetarget was 300 ppm. The “water” runs in Table 9 had the amount of wateradded that would be present in the charge of 85% phosphoric acid for atarget of 300 ppm phosphorus.

TABLE 9 % % Reduction AA Reduction P:Sb Free in Gen in XRF Mole IhV ItVAA Free 295/5 AA Sample # Additive Sb XRF P Ratio (dL/g) (dL/g) L* b*(ppm) AA (ppm) Gen 070 None 261 3 0 0.777 0.82 84.69 3.67 13.23 1 20.385.5 093 None 265 2 0 0.756 0.797 82.33 2.29 13.95 −4.4 20.765 3.7 117None 244 4 0.1 0.77 0.812 82.42 2.19 14.345 −7.3 22.265 −3.2 122 None258 3 0 0.767 0.809 82.13 2.8 11.94 10.7 22.85 −6.0 113 H3PO4 246 86 1.40.767 0.809 83.04 3.1 8.37 37.4 14.82 31.3 112 H3PO4 255 199 3.1 0.7080.743 81.3 2.57 7.765 41.9 18.135 15.9 116 H3PO4 249 300 4.7 0.653 0.68382.98 3.31 8.52 36.3 18.885 12.4 083 OPT 265 89 1.3 0.74 0.779 81.673.78 12.395 7.3 19.63 9.0 115 OPT 247 179 2.8 0.74 0.779 82.17 2.0410.69 20 20.985 2.7 085 OPT 264 257 3.8 0.713 0.749 82.76 2.27 12.1059.4 23.69 −9.9 132 OPT 266 278 4.1 0.684 0.717 83.69 2.56 12.815 4.123.84 −10.5 087 TBP 252 36 0.6 0.765 0.807 80.24 2.68 11.93 10.7 22.675−5.1 118 TBP 260 15 0.2 0.781 0.825 82.54 3.28 13.65 −2.1 21.36 1.0 091Water 258 3 0.0 0.741 0.78 80.07 2.32 10.9 18.4 23.74 −10.1 114 Water265 3 0 0.759 0.8 81.05 2.04 13.31 0.4 20.745 3.8 CB-12 0.79 18.28

Per Table 9, about 90 ppm phosphorus from phosphoric acid gives a lowerAA generation rate than about 200 or 300 ppm phosphorus from phosphoricacid. There is more It.V. loss at higher levels of phosphoric acid. FromExample 4, Sample #38, 150 ppm phosphorus from phosphoric acid does agood job lowering AA generation rate.

Example 10

Samples 11 & 17 prepared in Example 8 are solid-stated at 220° C. and0.5 mm Hg. Prior to solid-stating, pellets are sieved to be −6/+8 mesh.

TABLE 10 Starting SS Time Material (hours) Additive lhV (dL/g) ltV(dL/g) 11 0 89 ppm P from H3PO4 0.69 0.723 11 1 89 ppm P from H3PO40.686 0.719 11 2 89 ppm P from H3PO4 0.696 0.73  11 3 89 ppm P fromH3PO4 0.703 0.738 11 4 89 ppm P from H3PO4 0.714 0.75  11 6 89 ppm Pfrom H3PO4 0.742 0.781 11 8 89 ppm P from H3PO4 0.76 0.801 11 10 89 ppmP from H3PO4 0.784 0.828 11 12 89 ppm P from H3PO4 0.797 0.843 17 0 None0.712 0.748 17 1 None 0.736 0.774 17 2 None 0.771 0.813 17 3 None 0.7880.832 17 4 None 0.837 0.888 17 6 None 0.867 0.922 17 8 None 0.897 0.95617 10 None 0.981 1.052 17 12 None 1.014 1.091 11 0 89 ppm P from H3PO40.684 0:717 11 1 89 ppm P from H3PO4 0.684 0.717 11 2 89 ppm P fromH3PO4 0.697 0.731 11 3 89 ppm P from H3PO4 0.707 0.742 11 4 89 ppm Pfrom H3PO4 0.717 0.753 11 6 89 ppm P from H3PO4 0.744 0.783 11 8 89 ppmP from H3PO4 0.767 0.809 11 10 89 ppm P from H3PO4 0.773 0.816 11 12 89ppm P from H3PO4 0.8 0.846 17 0 None 0.715 0.751 17 1 None 0.737 0.77617 2 None 0.784 0.828 17 3 None 0.792 0.838 17 4 None 0.827 0.879 17 6None 0.888 0.945 17 8 None 0.952 1.019 17 10 None 0.976 1.047 17 12 None1.025 1.103

Solid-stating rate is decreased with the addition of an acidicphosphorus compound late. The extent of the decrease in solid-statingrate will depend on the P:Sb mole ratio. The sample without H3PO₄ tookabout 1.6 hours to reach 0.76 IhV while the sample with 90 ppm P fromH3PO₄ took about 8 hours to reach 0.76 IhV.

Example 11

Melt blending was done per procedures and details discussed in Example6, except the vacuum set points in stages 5, 6 & 7 are 0.5 mm Hg. Thepolymer used in Example 6 was used here and is identified by a catalystsystem of 230 ppm Sb & 8 ppm P. In addition, another commercialsolid-stated PET was used. It had the same target composition; however,its phosphorus level was higher per the identification by a catalystsystem of 230 ppm Sb & 55 ppm P.

TABLE 11 XRF AAGEN Catalyst Sb XRF P IhV 1 ItV Free AA 295/5 SampleSystem Additive (ppm) (ppm) (dL/g) (dL/g) (ppm) (ppm) CB-12 (ppm) . . .. 0.87 20.52 44 230 Sb& none 246 7 0.758 0.799 8.03 17.37 8 P 45 230 Sb&H3PO4 245 55 0.747 0.787 5.48 11.98 8 P 46 230 Sb none 226 55 0.7350.773 9.28 20.19 & 55 P 47 230 Sb& H3PO4 246 81 0.734 0.772 4.27 9.58 8P 48 230 Sb H3PO4 229 120 0.729 0.767 7.99 18.48 & 55 P 49 230 Sb& H3PO4243 94 0.726 0.763 4.17 11.12 8 P 50 230 Sb none 231 56 0.737 0.77610.74 22.41 & 55 P 55 230 Sb H3PO4 231 138 0.717 0.753 6.37 15.94 & 55 P52 230 Sb& none 243 7 0.761 0.802 9.01 17.23 8 P

In Table 11, to find the amount of phosphorus from the additive, theamount of phosphorus in polymer prior to phosphorus additive addition(see runs with no additive) is subtracted from number in the value XRF P(ppm). As it can be seen, when the starting polymer has less phosphorus,the late addition of a phosphorus compound is more effective at loweringAA generation rate.

What we claim is:
 1. Finished polyester polymer particles obtained by aprocess comprising polycondensing a molten polyester polymer compositionto an It.V. of at least 0.68dL/g; then adding at least one antimonycatalyst stabilizer or deactivator comprising an acidic phosphorouscompound to the polymer melt; and then solidifying the polymer melt intosolid polyester polymer particles, and having: a degree of crystallinityof at least 20%, antimony atoms, phosphorus atoms, an acetaldehydegeneration rate of less than 20 ppm, as measured at 295° C. for 5minutes, lacking organic acetaldehyde scavengers, and which have notbeen solid state polymerized, wherein the molar ratio of phosphorusatoms to antimony atoms, P:Sb, is at least 1:1.
 2. The finishedparticles of claim 1, wherein the particles have a residual acetaldehydelevel of 10 ppm or less.
 3. The finished particles of claim 1, whereinsaid finished particles comprise a bulk of particles.
 4. The finishedparticles of claim 3, wherein the bulk is contained in a shippingcontainer.
 5. The finished particles of claim 4, wherein the bulkoccupies a volume of at least 10 cubic meters.
 6. The finished particlesof claim 4, wherein the particles have an It.V. of at least 0.72 dL/gobtained in the melt phase and a degree of crystallinity of at least30%.
 7. The finished particles of claim 1, wherein the particles have ab* of 3 or less and an L* of 70 or more.
 8. The finished particles ofclaim 1, wherein the L* is 76 or more.
 9. The finished particles ofclaim 1, wherein the antimony atom content ranges from 150 ppm to 300ppm.
 10. The finished particles of claim 1, wherein the particles aredevoid of active titanium species.
 11. The finished particles of claim1, wherein the It.V. of the particles made in a melt phase production isat least 0.70 dL/g.
 12. The finished particles of claim 1, wherein thephosphorus atoms are obtained from an acidic phosphorus compound. 13.The finished particles of claim 12, wherein the phosphorus atoms areobtained from phosphoric acid.
 14. The finished particles of claim 1,wherein the level of residual acetaldehyde is 7 ppm or less.
 15. Thefinished particles of claim 1, wherein the molar ratio of phosphorusatoms to antimony atoms, P:Sb, is 1:1 to 2.1:1 and the phosphorus ispresent in the form of H₃PO₄.
 16. The finished particles of claim 1,wherein the molar ratio of phosphorus atoms to antimony atoms, P:Sb, is1.5:1 to 2.1:1 and the phosphorus is in the form of H₃PO₄.
 17. Thefinished particles of claim 1, wherein the molar ratio of phosphorusatoms to antimony atoms, P:Sb, is from 1.4:1 to 4.7:1 and the phosphorusis present in the form of H₃PO₄.
 18. The finished particles of claim 1,having an It.V that is within +/−0.05 dL/g of the molten polyesterpolymer composition.